Sustained-release nucleic acid matrix compositions

ABSTRACT

There are provided compositions for extended release of a nucleic acid agent, comprising a lipid-saturated matrix formed with a biodegradable polymer. Also provided are methods of producing the matrix compositions and methods for using the matrix compositions to provide controlled release of the nucleic acid agent.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. Ser. No. 13/574,040, which isa 35 U.S.C. §371 of PCT/IL2011/000054, filed Jan. 18, 2011, which claimsthe benefit of U.S. Ser. No. 61/296,040, filed Jan. 19, 2010. Thecontents of these applications are incorporated herein by reference.

FIELD OF THE INVENTION

The present invention provides compositions for extended and/orcontrolled release of nucleic acid based drugs/agents, comprising alipid-based matrix with a biocompatible polymer. The present inventionalso provides methods of producing the matrix compositions and methodsfor using the matrix compositions to provide controlled release of anucleic acid active agent.

BACKGROUND OF THE INVENTION

Therapeutic Nucleic Acids

Gene therapy is a major area of research in drug development. Genetherapy has been considered a desirable mechanism to correct geneticdefects resulting in diseases associated with failure to produce certainproteins and to overcome acquired diseases such as autoimmune diseasesand cancer. Gene therapy could provide a new prophylactic approach forthe treatment of many diseases. A technological barrier tocommercialization of gene therapy, however, is the need for practical,effective and safe means for polynucleotide delivery and sustainedand/or controlled release. Polynucleotides do not readily permeate thecellular membrane due to the charge repulsion between the negativelycharged membrane and the high negative charge on the polynucleotide. Asa result, polynucleotides have poor bioavailability and uptake intocells, typically <1%. In animal models, viral-based vectors have beenused successfully to administer genes to a desired tissue. In somecases, these approaches have led to long-term (>2 years) expression oftherapeutic levels of the protein. However, the limitations ofviral-based approaches have been extensively reported. For instance,re-administration is not possible with these vectors because of thehumoral immune response generated against the viral proteins. Inaddition to manufacturing challenges to obtain adequate reproduciblevector supply, there are also significant safety concerns associatedwith viral vectors, particularly for those targeting the liver for geneexpression. Not withstanding the problems associated with viral genetherapy, viruses have been considered by many to be more efficient thannon-viral delivery vehicles.

The silencing or down regulation of specific gene expression in a cellcan be affected by oligonucleic acids using techniques known asantisense therapy, RNA interference (RNAi), and enzymatic nucleic acidmolecules. Antisense therapy refers to the process of inactivatingtarget DNA or mRNA sequences through the use of complementary DNA or RNAoligonucleic acids, thereby inhibiting gene transcription ortranslation. An antisense molecule can be single stranded, doublestranded or triple helix. Other agents capable of inhibiting expressionare for example enzymatic nucleic acid molecules such as DNAzymes andribozymes, capable of specifically cleaving an mRNA transcript ofinterest. DNAzymes are single-stranded deoxyribonucleotides that arecapable of cleaving both single- and double-stranded target sequences.Ribozymes are catalytic ribonucleic acid molecules that are increasinglybeing used for the sequence-specific inhibition of gene expression bythe cleavage of mRNAs encoding proteins of interest. RNA interference isa method of post-transcriptional inhibition of gene expression that isconserved throughout many eukaryotic organisms. It helps to controlwhich genes are active and how active they are. Two types of small RNAmolecules—microRNA (miRNA) and small interfering RNA (siRNA)—are centralto RNA interference. RNAs are the direct products of genes, and thesesmall RNAs can bind to specific other RNAs and either increase ordecrease their activity, for example by preventing a messenger RNA fromproducing a protein. RNA interference has an important role in defendingcells against parasitic genes—viruses and transposons—but also indirecting development as well as gene expression in general. Althoughthe RNA interference effect, which is mediated by small interfering RNA(siRNA) or micro-RNA, has potential application to human therapy, thehydrodynamic method usually used for rapid administration ofoligonucleotides is unsuitable for use in humans. Development ofRNAi-based therapeutics is relatively new to the pharmaceuticalindustry. Although many of the obstacles to the development of suchdrugs have been overcome, optimal delivery of the RNAi compounds to theappropriate tissues and into the cells is still a challenge.

Delivery of Nucleic Acids

A problem of non-viral gene therapy is to achieve the delivery andexpression of sufficient nucleic acid to result in a tangible,physiologically relevant expression. Although DNA plasmids in isotonicsaline (so-called “naked” DNA) were shown several years ago to transfecta variety of cells in vivo, such unprotected plasmids are susceptible toenzymatic degradation leading to irreproducibility in uptake and highlyvariable expression and biological responses in animal models. The verylow bioavailability of “naked” plasmid in most tissues also requireshigh doses of plasmids to be administered to generate a pharmacologicalresponse. The field of non-viral gene delivery has therefore beendirected to the development of more efficient synthetic delivery systemscapable to increase the efficiency of plasmid delivery, confer prolongedexpression and provide for storage stable formulations as is expected ofother pharmaceutical formulations.

Chemical methods which facilitate the uptake of DNA by cells include theuse of DEAE-Dextran. However this can result in loss of cell viability.Calcium phosphate is also a commonly used chemical agent which, whenco-precipitated with DNA, introduces the DNA into cells.

Physical methods to introduce DNA have become effective means toreproducibly transfect cells. Direct microinjection is one such methodwhich can deliver DNA directly to the nucleus of a cell (Capecchi 1980,Cell, 22, 479). This allows the analysis of single cell transfectants.So called “biolistic” methods physically insert DNA into cells and/ororganelles using a high velocity particles coated with DNA.Electroporation is one of the most popular methods to transfect DNA. Themethod involves the use of a high voltage electrical charge tomomentarily permeabilize cell membranes making them permeable tomacromolecular complexes. However physical methods to introduce DNA doresult in considerable loss of cell viability due to intracellulardamage. More recently still a method termed immunoporation has become arecognized technique for the introduction of nucleic acid into cells,(Bildirici et al 2000, Nature, 405, 298). Transfection efficiency ofbetween 40-50% is achievable depending on the nucleic acid used. Thesemethods therefore require extensive optimization and also requireexpensive equipment.

To overcome the problem of degradation of nucleic acids, typicallyplasmid DNA (“pDNA”), or siRNAs/microRNA and enhance the efficiency ofgene transfection, cationic condensing agents (such as polybrene,dendrimers, chitosan, lipids, and peptides) have been developed toprotect the nucleic acids by condensing it through electrostaticinteractions. However, the use of condensed plasmid particles fortransfection of a large number of muscle cells in vivo, for example, hasnot been successful as compared to transfection of “naked” DNA.

Additional strategies that include the modulation of the plasmid surfacecharge and hydrophobicity by interaction with protective, interactivenon-condensing systems have shown advantages over the use of “naked” DNAfor direct administration to solid tissues (e.g., InternationalApplication Publication No. WO 96/21470).

Biodegradable microspheres that encapsulate the nucleic acid have alsobeen used in gene delivery. For example, International ApplicationPublication No. WO 00/78357 disclosed matrices, films, gels andhydrogels which include hyaluronic acid derivatized with a dihydrazideand crosslinked to a nucleic acid forming slow release microspheres.

Lipid based drug delivery systems are well known in the art ofpharmaceutical science. Typically they are used to formulate drugshaving poor bioavailability or high toxicity or both. Among theprevalent dosage forms that have gained acceptance are many differenttypes of liposomes, including small unilamellar vesicles, multilamellarvesicles and many other types of liposomes; different types ofemulsions, including water in oil emulsions, oil in water emulsions,water-in-oil-in-water double emulsions, submicron emulsions,microemulsions; micelles and many other hydrophobic drug carriers. Thesetypes of lipid based delivery systems can be highly specialized topermit targeted drug delivery or decreased toxicity or increasedmetabolic stability and the like. Extended release in the range of days,weeks and more are not profiles commonly associated with lipid baseddrug delivery systems in vivo. Liposomes that consist of amphiphiliccationic molecules are useful non-viral vectors for gene delivery invitro and in vivo. In theory, the cationic head of the lipid associateswith the negatively charged nucleic acid backbone of the DNA to formlipid:nucleic acid complexes. The lipid:nucleic acid complexes haveseveral advantages as gene transfer vectors. Unlike viral vectors, thelipid:nucleic acid complexes can be used to transfer expressioncassettes of essentially unlimited size. Since the complexes lackproteins, they may evoke fewer immunogenic and inflammatory responses.Moreover, they cannot replicate or recombine to form an infectious agentand have low integration frequency. The use of cationic lipids (e.g.liposomes) has become a common method since it does not have the degreeof toxicity shown by chemical methods.

There are a number of publications that demonstrate convincingly thatamphiphilic cationic lipids can mediate gene delivery in vivo and invitro, by showing detectable expression of a reporter gene in culturecells in vitro. Because lipid:nucleic acid complexes are on occasion notas efficient as viral vectors for achieving successful gene transfer,much effort has been devoted in finding cationic lipids with increasedtransfection efficiency (Gao et al., 1995, Gene Therapy 2, 710-722).

Several works have reported the use of amphiphilic cationiclipid:nucleic acid complexes for in vivo transfection both in animals,and in humans (reviewed in Thierry et al., Proc. Natl. Acad. Sci. USA1995, 92, 9742-9746). However, the technical problems for preparation ofcomplexes having stable shelf-lives have not been addressed. Forexample, unlike viral vector preparations, lipid:nucleic acid complexesare unstable in terms of particle size. It is therefore difficult toobtain homogeneous lipid:nucleic acid complexes with a size distributionsuitable for systemic injection. Most preparations of lipid:nucleic acidcomplexes are metastable. Consequently, these complexes typically mustbe used within a short period of time ranging from 30 minutes to a fewhours. In clinical trials using cationic lipids as a carrier for DNAdelivery, the two components were mixed at the bed-side and usedimmediately. The structural instability along with the loss oftransfection activity of lipid:nucleic acid complex with time have beenchallenges for the future development of lipid-mediated gene therapy.Many of the recent developments in the field have focused onmodification of the cationic system by combining a proven cationicdelivery agent with another moiety. However, cationic backboneconjugates have not been successful in overcoming toxicity and none areapproved for therapeutic use.

International Application Publication No. WO 95/24929 disclosedencapsulation or dispersion of genes in a biocompatible matrix,preferably biodegradable polymeric matrix, where the gene is able todiffuse out of the matrix over an extended period of time. Preferablythe matrix is in the form of a microparticle such as a microsphere,microcapsule, a film, an implant, or a coating on a device such as astent.

U.S. Pat. No. 6,048,551 disclosed a controlled release gene deliverysystem utilizing poly(lactide-co-glycolide) (PLGA), hydroxypropylmethylcellulose phthalate, cellulose acetate phthalate, and the Ludragit R, L,and E series of polymers and copolymer microspheres to encapsulate thegene vector.

U.S. Application Publication No. 20070141134 discloses compositions thatenhance the intracellular delivery of polynucleotides, wherein apolynucleotide can be incorporated into a PEG shielded micelle particleto facilitate the delivery of the polynucleotide across a cellularmembrane. Incorporation of the polynucleotide into the shielded micelleparticle is provided by covalent and non-covalent means. Other celltargeting agents may also be covalently coupled to the shielded micelleparticle to enhance localization in the body.

International Patent Application Publication No. WO 2008/124634discloses a method for encapsulating nucleic acids, particularly siRNAs,shRNAs, microRNAs, gene therapy plasmids, and other oligonucleotides inbiodegradable polymer, whereby the nucleic acids are formulated intoreverse micelles composed of non-toxic and/or naturally-occurring lipidsprior to nanoparticle formation by nanoprecipitation.

International Application Publication No. WO 2009/127060 discloses anucleic acid-lipid particle, comprising, in addition to the nucleicacid, a cationic lipid, a non-cationic lipid and a conjugated lipid thatinhibits aggregation of the particles.

International Patent Application Publication No. WO 2010/007623 to someinventors of the present invention, published after the priority date ofthe present invention, discloses compositions for extended release ofhydrophobic molecules such as steroids and antibiotics, comprising alipid-based matrix comprising a biodegradable polymer.

Ideally sustained release drug delivery systems should exhibit kineticand other characteristics readily controlled by the types and ratios ofthe specific excipients used. There remain an unmet need for improvednucleic acid compositions and methods for controlled and extendeddelivery of therapeutic nucleic acid agents to appropriate tissues andinto cells for gene therapy. Nowhere in the prior art it was suggestedthat matrix compositions comprising lipids and biocompatible polymerwill possess improved properties for delivering nucleic acid basedagents.

SUMMARY OF THE INVENTION

The present invention provides compositions for extended release ofnucleic acid agents, particularly nucleic acid-based drugs, comprising alipid-based matrix comprising a biocompatible polymer. The matrixcomposition is particularly suitable for local delivery or localapplication of a nucleic acid agent. The present invention also providesmethods of producing the matrix compositions and methods for using thematrix compositions to provide controlled and/or sustained release of anactive nucleic-acid ingredient.

The present invention is based in part on the unexpected discovery thatnegatively charged nucleic acids present in a water-based solutioncomprising polyethylene glycol (PEG) can be efficiently loaded into alipid-based matrix comprising at least one biocompatible polymer,wherein the polymer can be biodegradable polymer, non-biodegradablepolymer or a combination thereof. Furthermore, the nucleic acid can bereleased from the matrix in a controlled and/or extended manner.

The matrix compositions of the present invention is advantageous overhitherto known compositions and matrices for nucleic acid delivery inthat it combines efficient local delivery of nucleic acid agent to cellsor tissues with controlled and/or sustained release of the nucleic acidagent.

In one aspect, the present invention provides a matrix compositioncomprising: (a) a pharmaceutically acceptable biocompatible polymer inassociation with a first lipid component comprising at least one lipidhaving a polar group; (b) a second lipid component comprising at leastone phospholipid having fatty acid moieties of at least 14 carbons; (c)at least one nucleic acid agent and (d) polyethylene glycol (PEG),wherein the matrix composition is adapted for providing sustained and/orcontrolled release of the nucleic acid.

Any nucleic acid molecule having a therapeutic or diagnostic utility maybe used as part of the matrix compositions of the present invention. Thenucleic acid agent may include DNA molecules, RNA molecules, single,double, triple or quadruple stranded. Non-limitative list of nucleicacid agent includes: plasmid DNA, linear DNA, (poly- andoligo-nucleotide), chromosomal DNA, messenger RNA (mRNA), antisenseDNA/RNA, RNAi, siRNA, microRNA (miRNA), ribosomal RNA, locked nucleicacid analogue (LNA), oligonucleotide DNA (ODN) single and doublestranded, imunostimulating sequences (ISS), and ribozymes.

The nucleic acid agent according to the present invention may includenatural molecules, modified molecules or artificial molecules.

According to certain embodiments, the nucleic acid has non covalentinteractions with PEG.

According to certain embodiments, the PEG is a linear PEG having amolecular weight in the range of 1,000-10,000. According to typicalembodiments, the PEG molecular weight is in the range of 1,000-8,000,more typically below 8,000. Biodegradable PEG molecules, particularlyPEG molecules comprising degradable spacers having higher molecularweights can be also used according to the teachings of the presentinvention.

PEG molecules having a molecular weight of 5,000 or less are currentlyapproved for pharmaceutical use. Thus, according to certain typicalembodiments, the active PEG molecules have a molecular weight of up to5,000.

According to some embodiments the matrix composition comprises at leastone cationic lipid. According to certain embodiments, the cationic lipidis selected from the group consisting of DC-Cholesterol,1,2-dioleoyl-3-trimethylammonium-propane (DOTAP),Dimethyldioctadecylammonium (DDAB),1,2-dilauroyl-sn-glycero-3-ethylphosphocholine (Ethyl PC),1,2-di-O-octadecenyl-3-trimethylammonium propane (DOTMA), and others.Each possibility represents a separate embodiment of the presentinvention.

According to certain embodiments, the biocompatible polymer is selectedfrom the group consisting of biodegradable polymer, non-biodegradablepolymer and a combination thereof. According to certain embodiments thebiodegradable polymer comprises polyester selected from the groupconsisting of PLA (polylactic acid), PGA (poly glycolic acid), PLGA(poly(lactic-co-glycolic acid)) and combinations thereof. According toother embodiments, the non-biodegradable polymer is selected from thegroup consisting of polyethylene glycol (PEG), PEG acrylate, PEGmethacrylate, methylmethacrylate, ethylmethacrylate, butylmethacrylate,2-ethylhexylmethacrylate, laurylmethacrylate, hydroxylethylmethacrylate, 2-methacryloyloxyethylphosphorylcholine (MPC),polystyrene, derivatized polystyrene, polylysine, polyN-ethyl-4-vinyl-pyridinium bromide, poly-methylacrylate, silicone,polyoxymethylene, polyurethane, polyamides, polypropylene, polyvinylchloride, polymethacrylic acid, and derivatives thereof alone or asco-polymeric mixtures thereof. Each possibility represents a separateembodiment of the present invention.

According to additional embodiments, the non-biodegradable polymer andthe biodegradable polymer form a block co-polymer, for example,PLGA-PEG-PLGA and the like.

According to certain embodiments the lipid having a polar group isselected from the group consisting of a sterol, a tocopherol and aphosphatidylethanolamine According to certain particular embodiments,the lipid having a polar group is sterol or a derivative thereof.According to typical embodiments, the sterol is cholesterol.

According to certain embodiments the first lipid component is mixed withthe biocompatible polymer to form a non-covalent association.

According to certain particular embodiments, the first lipid componentis sterol or a derivative thereof and the bio-compatible polymer isbiodegradable polyester. According to these embodiments, thebiodegradable polyester is associated with the sterol via non-covalentbonds.

According to some embodiments the second lipid component comprises aphosphatidylcholine or a derivative thereof. According to otherembodiments the second lipid component comprises a mixture ofphosphatidylcholines or derivatives thereof. According to yet otherembodiments the second lipid component comprises a mixture of aphosphatidylcholine and a phosphatidylethanolamine or derivativesthereof. According to additional embodiments, the second lipid componentfurther comprises a sterol and derivatives thereof. According to typicalembodiments, the sterol is cholesterol. According to yet furtherembodiments the second lipid component comprises a mixture ofphospholipids of various types. According to certain typicalembodiments, the second lipid component further comprises at least oneof a sphingolipid, a tocopherol and a pegylated lipid.

According to additional embodiments, the weight ratio of the totallipids to the biocompatible polymer is between 1:1 and 9:1 inclusive.

According to certain embodiments, the matrix composition is homogeneous.In other embodiments, the matrix composition is in the form of alipid-based matrix whose shape and boundaries are determined by thebiodegradable polymer. In yet further embodiments, the matrixcomposition is in the form of an implant.

In certain particular embodiments, the present invention provides amatrix composition comprising: (a) biodegradable polyester; (b) asterol; (c) a phosphatidylethanolamine having fatty acid moieties of atleast 14 carbons; (d) a phosphatidylcholine having fatty acid moietiesof at least 14 carbons; (e) a nucleic acid agent and (f) PEG.

In certain embodiments the matrix composition comprises at least 50%lipid by weight. In certain additional embodiments, the matrixcomposition further comprises a targeting moiety.

In certain embodiments, the matrix composition is capable of beingdegraded in vivo to vesicles into which some or all the mass of thereleased nucleic acid is integrated. In other embodiments, the matrixcomposition is capable of being degraded in vivo to form vesicles intowhich the active agent and the targeting moiety are integrated. Eachpossibility represents a separate embodiment of the present invention.

According to an additional aspect the present invention provides apharmaceutical composition comprising the matrix composition of thepresent invention and a pharmaceutically acceptable excipient.

According to certain embodiments, the matrix composition of the presentinvention is in the form of an implant, following removal of the organicsolvents and water. In another embodiment, the implant is homogeneous.Each possibility represents a separate embodiment of the presentinvention.

According to certain embodiments, the process of creating an implantfrom a composition of the present invention comprises the steps of (a)creating a matrix composition according to a method of the presentinvention in the form of a bulk material; and (b) transferring the bulkmaterial into a mold or solid receptacle of a desired shaped.

According to another aspect the present invention provides a method forproducing a matrix composition for delivery and sustained and/orcontrolled release of a nucleic acid agent comprising:

(a) mixing into a first volatile organic solvent (i) a biocompatiblepolymer and (ii) a first lipid component comprising at least one lipidhaving a polar group;

(b) mixing polyethylene glycol into a water-based solution of thenucleic acid agent;

(c) mixing the solution obtained in step (b) with a second volatileorganic solvent and a second lipid component comprising at least onephospholipid having fatty acid moieties of at least 14 carbons;

(d) mixing the solutions obtained in steps (a) and (c) to form ahomogeneous mixture; and

(e) removing the volatile solvents and water,

thereby producing a homogeneous polymer-phospholipids matrix comprisingthe nucleic acid agent.

According to certain embodiments, step (c) optionally further comprises(i) removing the solvents by evaporation, freeze drying orcentrifugation to form a sediment; and (ii) suspending the resultingsediment in the second volatile organic solvent.

The selection of the specific solvents is made according to the specificnucleic acid and other substances used in the particular formulation andthe intended use of the active nucleic acid, and according toembodiments of the present invention described herein. The particularlipids forming the matrix of the present invention are selectedaccording to the desired release rate of the nucleic acids and accordingto embodiments of the present invention described herein.

The solvents are typically removed by evaporation conducted atcontrolled temperature determined according to the properties of thesolution obtained. Residues of the organic solvents and water arefurther removed using vacuum.

According to the present invention the use of different types ofvolatile organic solutions enable the formation of homogeneouswater-resistant, lipid based matrix compositions. According to variousembodiments the first and second solvents can be the same or different.According to some embodiments one solvent can be non-polar and the otherpreferably water-miscible.

According to certain embodiments, the matrix composition issubstantially free of water. The term “substantially free of water”refers to a composition containing less than 1% water by weight. Inanother embodiment, the term refers to a composition containing lessthan 0.8% water by weight. In another embodiment, the term refers to acomposition containing less than 0.6% water by weight. In anotherembodiment, the term refers to a composition containing less than 0.4%water by weight. In another embodiment, the term refers to a compositioncontaining less than 0.2% water by weight. In another embodiment, theterm refers to the absence of amounts of water that affect thewater-resistant properties of the matrix. Each possibility represents aseparate embodiment of the present invention.

In other embodiments, the matrix composition is essentially free ofwater. “Essentially free” refers to a composition comprising less than0.1% water by weight. In another embodiment, the term refers to acomposition comprising less than 0.08% water by weight. In anotherembodiment, the term refers to a composition comprising less than 0.06%water by weight. In another embodiment, the term refers to a compositioncomprising less than 0.04% water by weight. In another embodiment, theterm refers to a composition comprising less than 0.02% water by weight.In another embodiment, the term refers to a composition comprising lessthan 0.01% water by weight. Each possibility represents a separateembodiment of the present invention.

In another embodiment, the matrix composition is free of water. Inanother embodiment, the term refers to a composition not containingdetectable amounts of water. Each possibility represents a separateembodiment of the present invention.

According to certain typical embodiments, the present invention providesa method of producing a matrix composition, the method comprising thesteps of

(a) mixing into a non-polar volatile organic solvent (i) a biodegradablepolyester and (ii) a sterol;

(b) mixing polyethylene glycol having a molecular weight in the range of1,000-8,000 into a water-based solution of the nucleic acid agent;

(c) mixing the solution obtained in step (b) with a water-misciblevolatile organic solvent containing phosphatidylethanolamine and/orphosphatidylcholine and/or sterol; and

(d) mixing the solutions obtained in steps (a) and (c) to form ahomogeneous mixture;

(e) removing the organic solvents and water; and

(f) further removing the remaining solvent by vacuum.

According to certain embodiments, the biodegradable polyester isselected from the group consisting of PLA, PGA and PLGA. In otherembodiments, the biodegradable polyester is any other suitablebiodegradable polyester or polyamine known in the art. In yet additionalembodiments, the mixture containing the non-polar, organic solvent ishomogenized prior to mixing it with the water-miscible volatile organicsolvent mixture. In other embodiments, the mixture containing thewater-miscible, organic solvent is homogenized prior to mixing it withthe mixture containing the non-polar, organic solvent. In certainembodiments, the polymer in the mixture of step (a) is lipid saturated.In additional embodiments, the matrix composition is lipid saturated.Each possibility represents a separate embodiment of the presentinvention.

The matrix composition of the present invention can be used for coatingfully or partially the surface of different substrates. According tocertain embodiments, substrates to be coated include at least onematerial selected from the group consisting of carbon fibers, stainlesssteel, cobalt-chromium, titanium alloy, tantalum, ceramic and collagenor gelatin. In other embodiments substrates may include any medicaldevices and bone filler particles. Bone filler particles can be any oneof allogeneic (i.e., from human sources), xenogeneic (i.e., from animalsources) and artificial bone particles. In other embodiments a treatmentusing the coated substrates and administration of the coated substrateswill follow procedures known in the art for treatment and administrationof similar uncoated substrates.

It is to be emphasized that the sustained release period using thecompositions of the present invention can be programmed taking intoaccount four major factors: (i) the weight ratio between the polymer andthe lipid content, specifically the phospholipid having fatty acidmoieties of at least 14 carbons, (ii) the biochemical and/or biophysicalproperties of the biopolymer and the lipids; (iii) the ratio between thedifferent lipids used in a given composition and (iv) the incubationtime of the nucleic acid agent with polyethylene glycol.

Specifically, the degradation rate of the polymer and the fluidity ofthe lipid should be considered. For example, a PLGA (85:15) polymer willdegrade slower than a PLGA (50:50) polymer. A phosphatidylcholine (14:0)is more fluid (less rigid and less ordered) at body temperature than aphosphatidylcholine (18:0). Thus, for example, the release rate of anucleic acid agent incorporated in a matrix composition comprising PLGA(85:15) and phosphatidylcholine (18:0) will be slower than that of anucleic acid agent incorporated in a matrix composed of PLGA (50:50) andphosphatidylcholine (14:0). Another aspect that will determine therelease rate is the physical characteristics of the nucleic acids. Inaddition, the release rate of a nucleic acid agent, particularly nucleicacid based drug can further be controlled by the addition of otherlipids into the formulation of the second lipid component. This canincludes fatty acids of different length such as lauric acid (C12:0),membrane active sterols (such as cholesterol) or other phospholipidssuch as phosphatidylethanolamine. The incubation time of the nucleicacid agent with polyethylene glycol affects the release rate of thenucleic acids from the matrix. Longer incubation time, at the range ofseveral hours leads to higher release rate. According to variousembodiments the active agent is released from the composition over adesired period ranging between several days to several months.

According to certain embodiments, at least 30% of the nucleic acid basedagent is released from the matrix composition at zero-order kinetics.According to other embodiments, at least 50% of the nucleic acid basedagent is released from the composition at zero-order kinetics.

These and other features and advantages of the present invention willbecome more readily understood and appreciated from the detaileddescription of the invention that follows.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a standard curve showing the relation between ssDNAconcentration and the fluorescence intensity of the fluorescent probelinked to the 5′ end of the ssDNA

FIG. 2 demonstrates the release rate over time (days) of ssDNA loadedinto a matrix composition prepared without polyethylene glycol (PEG).The release rate was normalized to the estimated amount of ssDNA loaded.

FIGS. 3A and 3B represents light microscopy (×400) pictures of lipidvesicles released following hydration of ssDNA from a matrix compositiondescribed in example 2. FIG. 3A demonstrates a typical lipid vesiclesreleased into the medium following hydration. FIG. 3B shows a greenfluorescence emission from the same vesicles indicating that thesevesicles contained the florescent probe.

FIG. 4 shows an agarose gel of PCR products amplified with the ssDNAreleased from the matrix composition.

FIG. 5 shows the size of ssDNA released from the matrix compositionmeasured by GeneScan analysis.

FIG. 6 demonstrates the release rate over time (days) of ssDNA loadedinto a matrix composition prepared with polyethylene glycol (PEG) atdifferent incubation times of the ssDNA and PEG.

FIG. 7 demonstrates the effect of using phospholipids with differentlength of fatty acid chains as the main lipid within the matrixcomposition on the release rate of the loaded ssDNA.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides compositions for extended and/orcontrolled release of nucleic-acids, comprising a lipid-based matrixwith a biocompatible polymer. Particularly, the matrix compositions ofthe present invention are suitable for local release of the nucleicacids. The present invention also provides methods of producing thematrix compositions and methods for using the matrix compositions toprovide controlled release of an active ingredient in the body of asubject in need thereof.

According to one aspect, the present invention provides a matrixcomposition comprising: (a) a pharmaceutically acceptable biocompatiblepolymer in association with a first lipid component comprising at leastone lipid having a polar group; (b) a second lipid component comprisingat least one phospholipid having fatty acid moieties of at least 14carbons; (c) at least one nucleic acid agent; and (d) polyethyleneglycol (PEG), wherein the matrix composition is adapted for providingsustained release of the nucleic acids.

According to certain embodiments, the biocompatible polymer isbiodegradable. According to other embodiments, the biocompatible polymeris non-biodegradable. According to additional embodiments, thebiocompatible polymer comprises a combination of biodegradable andnon-biodegradable polymers, optionally as block co-polymer.

According to certain embodiments, the present invention provides amatrix composition comprising: (a) pharmaceutically acceptablebiodegradable polyester; (b) a phospholipid having fatty acid moietiesof at least 14 carbons: (c) a pharmaceutically active nucleic acidagent; and (d) PEG.

The nucleic acid agent comprises any nucleic acid molecule having atherapeutic or diagnostic utility. According to some embodiments thenucleic acid agent comprises a DNA molecule, an RNA molecule, single,double, triple or quadruple stranded. According to other embodiments thenucleic acid based agent is selected from the group consisting of:plasmid DNA, linear DNA, (poly- and oligo-nucleotide), chromosomal DNA,messenger RNA (mRNA), antisense DNA/RNA, RNAi, siRNA, microRNA (miRNA),ribosomal RNA, locked nucleic acid analogue (LNA), oligonucleotide DNA(ODN) single and double stranded, imunostimulating sequence (ISS), andribozymes. According to certain typical embodiments, the nucleic acidagent is for therapeutic use.

According to some embodiments the lipid-saturated matrix compositioncomprises at least one cationic lipid. The term “cationic lipid” refersto any of a number of lipid species that carry a net positive charge ata selected pH, such as physiological pH. Such lipids include, but arenot limited to, N,N-dioleyl-N,N-dimethylammonium chloride (“DODAC”);N-(2,3-dioleyloxy)propyl)-N,N,N-trimethylammonium chloride (“DOTMA”);N,N-distearyl-N,N-dimethylammonium bromide (“DDAB”);N-(2,3-dioleoyloxy)propyl)-N,N,N-trimethylammonium chloride (“DOTAP”);3-(N—(N′,N′-dimethylaminoethane)carbamoyl)cholesterol (“DC-Chol”) andN-(1,2-dimyristyloxyprop-3-yl)-N,N-dimethyl-N-hydroxyethyl ammoniumbromide (“DMRIE”). Additionally, a number of commercial preparations ofcationic lipids are available which can be used in the presentinvention. These include, for example, LIPOFECTIN® (commerciallyavailable cationic liposomes comprising DOTMA and1,2-dioleoyl-sn-3-phosphoethanolamine (“DOPE”), from GIBCO/BRL, GrandIsland, N.Y., USA); LIPOFECTAMINE® (commercially available cationicliposomes comprisingN-(1-(2,3-dioleyloxy)propyl)-N-(2-(sperminecarboxamido)ethyl)N,N-dimethylammoniumtrifluoroacetate (“DOSPA”) and (“DOPE”), from GIBCO/BRL); andTRANSFECTAM® (commercially available cationic lipids comprisingdioctadecylamidoglycyl carboxyspermine (“DOGS”) in ethanol from PromegaCorp., Madison, Wis., USA). The following lipids are cationic and have apositive charge at below physiological pH: DODAP, DODMA, DMDMA and thelike. Without wishing to be bound by any specific theory or mechanism ofaction, the cationic lipids of the matrix facilitate the internalizationof the matrix of the invention, comprising nucleic acid agent, intocells or tissues. According to certain embodiments, the cells and/ortissues form part of the human body.

According to other embodiments the biodegradable polymer comprisescationic polymers, such as cationized guar gum, diallyl quaternaryammonium salt/acrylamide copolymers, quaternized polyvinylpyrrolidoneand derivatives thereof, and various polyquaternium-compounds.

According to certain embodiments, the phospholipid of the second lipidcomponent is a phosphatidylcholine having fatty acid moieties of atleast 14 carbons. In another embodiment, the of the second lipidcomponent further comprises a phosphatidylethanolamine having fatty acidmoieties of at least 14 carbons. In another embodiment, the of thesecond lipid component further comprises sterol, particularlycholesterol.

In certain embodiments, the matrix composition is lipid saturated.“Lipid saturated,” as used herein, refers to saturation of the polymerof the matrix composition with lipids including phospholipids, incombination with any nucleic acid agent and optionally a targetingmoiety present in the matrix, and any other lipids that may be present.The matrix composition is saturated by whatever lipids are present.Lipid-saturated matrices of the present invention exhibit the additionaladvantage of not requiring a synthetic emulsifier or surfactant such aspolyvinyl alcohol; thus, compositions of the present invention aretypically substantially free of polyvinyl alcohol. Methods fordetermining the polymer:lipid ratio to attain lipid saturation andmethods of determining the degree of lipid saturation of a matrix areknown in the art.

In other embodiments, the matrix composition is homogeneous. In yetadditional embodiments, the matrix composition is in the form of alipid-saturated matrix whose shape and boundaries are determined by thebiodegradable polymer. According to certain embodiments, the matrixcomposition is in the form of an implant.

In certain particular embodiments, the present invention provides amatrix composition comprising: (a) biodegradable polyester; (b) asterol; (c) a phosphatidylethanolamine having fatty acid moieties of atleast 14 carbons; (d) a phosphatidylcholine having fatty acid moietiesof at least 14 carbons; (e) at least one nucleic acid based drug, and(f) PEG. In other typical embodiments, the matrix composition is lipidsaturated.

In other typical embodiments, the present invention provides a matrixcomposition comprising: (a) biodegradable polyester; (b) a sterol; (c) aphosphatidylethanolamine having fatty acid moieties of at least 14carbons; (d) a phosphatidylcholine having fatty acid moieties of atleast 14 carbons; (e) a nucleic acid based active agent; and (f) PEG.

According to certain embodiments, the biodegradable polyester isassociated with the sterol via non-covalent bonds.

As provided herein, the matrix of the present invention is capable ofbeing molded into three-dimensional configurations of varying thicknessand shape. Accordingly, the matrix formed can be produced to assume aspecific shape including a sphere, cube, rod, tube, sheet, or intostrings. In the case of employing freeze-drying steps during thepreparation of the matrix, the shape is determined by the shape of amold or support which may be made of any inert material and may be incontact with the matrix on all sides, as for a sphere or cube, or on alimited number of sides as for a sheet. The matrix may be shaped in theform of body cavities as required for implant design. Removing portionsof the matrix with scissors, a scalpel, a laser beam or any othercutting instrument can create any refinements required in thethree-dimensional structure. Each possibility represents a separateembodiment of the present invention.

According to additional embodiments, the matrix composition of thepresent invention provides a coating of bone graft material. Accordingto certain embodiment, the bone graft material is selected from thegroup consisting of an allograft, an alloplast, and xenograft. Accordingto further embodiments the matrix of the present invention can becombined with a collagen or collagen matrix protein.

Lipids

“Phosphatidylcholine” refers to a phosphoglyceride having aphosphorylcholine head group. Phosphatidylcholine compounds, in anotherembodiment, have the following structure:

The R and R′ moieties are fatty acids, typically naturally occurringfatty acids or derivatives of naturally occurring fatty acids. In someembodiments, the fatty acid moieties are saturated fatty acid moieties.In some embodiments, the fatty acid moieties are unsaturated fatty acidmoieties. “Saturated”, refers to the absence of a double bond in thehydrocarbon chain. In another embodiment, the fatty acid moieties haveat least 14 carbon atoms. In another embodiment, the fatty acid moietieshave 16 carbon atoms. In another embodiment, the fatty acid moietieshave 18 carbon atoms. In another embodiment, the fatty acid moietieshave 16-18 carbon atoms. In another embodiment, the fatty acid moietiesare chosen such that the gel-to-liquid-crystal transition temperature ofthe resulting matrix is at least 40° C. In another embodiment, the fattyacid moieties are both palmitoyl. In another embodiment, the fatty acidmoieties are both stearoyl. In another embodiment, the fatty acidmoieties are both arachidoyl. In another embodiment, the fatty acidmoieties are palmitoyl and stearoyl. In another embodiment, the fattyacid moieties are palmitoyl and arachidoyl. In another embodiment, thefatty acid moieties are arachidoyl and stearoyl. In another embodiment,the fatty acid moieties are both myristoyl. Each possibility representsa separate embodiment of the present invention.

In another embodiment, the phosphatidylcholine is a naturally-occurringphosphatidylcholine. In another embodiment, the phosphatidylcholine is asynthetic phosphatidylcholine. In another embodiment, thephosphatidylcholine contains a naturally-occurring distribution ofisotopes. In another embodiment, the phosphatidylcholine is a deuteratedphosphatidylcholine. Typically, the phosphatidylcholine is a symmetricphosphatidylcholine (i.e. a phosphatidylcholine wherein the two fattyacid moieties are identical). In another embodiment, thephosphatidylcholine is an asymmetric phosphatidylcholine.

Non-limiting examples of phosphatidylcholines are1,2-distearoyl-sn-glycero-3-phosphocholine (DSPC),Dipalmitoyl-phosphatidylcholine (DPPC), Dimyristoyl-phosphatidylcholine(DMPC), dioleoyl-phosphatidylcholine (DOPC),1-palmitoyl-2-oleoyl-phosphatidylcholine, and phosphatidylcholinesmodified with any of the fatty acid moieties enumerated hereinabove. Incertain embodiments, the phosphatidylcholine is selected from the groupconsisting of DSPC, DPPC and DMPC. In another embodiment, thephosphatidylcholine is any other phosphatidylcholine known in the art.Each phosphatidylcholine represents a separate embodiment of the presentinvention.

Non-limiting examples of deuterated phosphatidylcholines are deuterated1,2-distearoyl-sn-glycero-3-phosphocholine (deuterated DSPC), deuterateddioleoyl-phosphatidylcholine (deuterated DOPC), and deuterated1-palmitoyl-2-oleoyl-phosphatidyl choline. In another embodiment, thephosphatidylcholine is selected from the group consisting of deuteratedDSPC, deuterated DOPC, and deuterated1-palmitoyl-2-oleoyl-phosphatidylcholine. In another embodiment, thephosphatidylcholine is any other deuterated phosphatidylcholine known inthe art.

In certain embodiments, the phosphatidylcholine(s) (PC) compose at least30% of the total lipid content of the matrix composition. In otherembodiments, PC(s) compose at least 35% of the total lipid content,alternatively at least 40% of the total lipid content, yet alternativelyat least 45%, at least 50%, least 55%, least 60%, at least 65%, at least70%, at least 75%, at least 80%, at least 85%, at least 90% or at least95% of the total lipid content. In another embodiment, PC(s) composeover 95% of the total lipid content. Each possibility represents aseparate embodiment of the present invention.

“Phosphatidylethanolamine” refers to a phosphoglyceride having aphosphoryl ethanolamine head group. Phosphatidylethanolamine compounds,in another embodiment, have the following structure:

The R and R′ moieties are fatty acids, typically naturally occurringfatty acids or derivatives of naturally occurring fatty acids. Inanother embodiment, the fatty acid moieties are saturated fatty acidmoieties. “Saturated” in another embodiment, refers to the absence of adouble bond in the hydrocarbon chain. In another embodiment, the fattyacid moieties have at least 14 carbon atoms. In another embodiment, thefatty acid moieties have at least 16 carbon atoms. In anotherembodiment, the fatty acid moieties have 14 carbon atoms. In anotherembodiment, the fatty acid moieties have 16 carbon atoms. In anotherembodiment, the fatty acid moieties have 18 carbon atoms. In anotherembodiment, the fatty acid moieties have 14-18 carbon atoms. In anotherembodiment, the fatty acid moieties have 14-16 carbon atoms. In anotherembodiment, the fatty acid moieties have 16-18 carbon atoms. In anotherembodiment, the fatty acid moieties are chosen such that thegel-to-liquid-crystal transition temperature of the resulting matrix isat least 40° C. In another embodiment, the fatty acid moieties are bothmyristoyl. In another embodiment, the fatty acid moieties are bothpalmitoyl. In another embodiment, the fatty acid moieties are bothstearoyl. In another embodiment, the fatty acid moieties are botharachidoyl. In another embodiment, the fatty acid moieties are myristoyland stearoyl. In another embodiment, the fatty acid moieties aremyristoyl and arachidoyl. In another embodiment, the fatty acid moietiesare myristoyl and palmitoyl. In another embodiment, the fatty acidmoieties are palmitoyl and stearoyl. In another embodiment, the fattyacid moieties are palmitoyl and arachidoyl. In another embodiment, thefatty acid moieties are arachidoyl and stearoyl. Each possibilityrepresents a separate embodiment of the present invention.

In another embodiment, the phosphatidylethanolamine is anaturally-occurring phosphatidylethanolamine. In another embodiment, thephosphatidylethanolamine is a synthetic phosphatidylethanolamine. Inanother embodiment, the phosphatidylethanolamine is a deuteratedphosphatidylethanolamine. In another embodiment, thephosphatidylethanolamine contains a naturally-occurring distribution ofisotopes. Typically the phosphatidylethanolamine is a symmetricphosphatidylethanolamine. In another embodiment, thephosphatidylethanolamine is an asymmetric phosphatidylethanolamine.

Non-limiting examples of phosphatidylethanolamines are dimethyldimyristoyl phosphatidylethanolamine (DMPE) anddipalmitoyl-phosphatidylethanolamine (DPPE), andphosphatidylethanolamines modified with any of the fatty acid moietiesenumerated hereinabove. In another embodiment, thephosphatidylethanolamine is selected from the group consisting of DMPEand DPPE.

Non-limiting examples of deuterated phosphatidylethanolamines aredeuterated DMPE and deuterated DPPE. In another embodiment, thephosphatidylethanolamine is selected from the group consisting ofdeuterated DMPE and deuterated DPPE. In another embodiment, thephosphatidylethanolamine is any other deuteratedphosphatidylethanolamine known in the art.

In another embodiment, the phosphatidylethanolamine is any otherphosphatidylethanolamine known in the art. Each phosphatidylethanolaminerepresents a separate embodiment of the present invention.

“Sterol” in one embodiment refers to a steroid with a hydroxyl group atthe 3-position of the A-ring. In another embodiment, the term refers toa steroid having the following structure:

In another embodiment, the sterol of methods and compositions of thepresent invention is a zoosterol. In another embodiment, the sterol ischolesterol:

In another embodiment, the sterol is any other zoosterol known in theart. In another embodiment, the moles of sterol are up to 40% of themoles of total lipids present. In another embodiment, the sterol isincorporated into the matrix composition. Each possibility represents aseparate embodiment of the present invention.

In another embodiment, the cholesterol is present in an amount of 10-60percentage of the total weight of lipid content of the matrixcomposition. In another embodiment, the weight percentage is 20-50%. Inanother embodiment, the weight percentage is 10-40%. In anotherembodiment, the weight percentage is 30-50%. In another embodiment, theweight percentage is 20-60%. In another embodiment, the weightpercentage is 25-55%. In another embodiment, the weight percentage is35-55%. In another embodiment, the weight percentage is 30-60%. Inanother embodiment, the weight percentage is 30-55%. In anotherembodiment, the weight percentage is 20-50%. In another embodiment, theweight percentage is 25-55%. Each possibility represents a separateembodiment of the present invention.

In another embodiment, a composition of the present invention furthercomprises a lipid other than phosphatidylcholine,phosphatidylethanolamine, or a sterol. According to certain embodiments,the additional lipid is a phosphoglyceride. According to otherembodiments, the additional lipid is selected from the group consistingof a phosphatidylserine, a phosphatidylglycerol, and aphosphatidylinositol. In yet additional embodiments, the additionallipid is selected from the group consisting of a phosphatidylserine, aphosphatidylglycerol, a phosphatidylinositol, and a sphingomyelin.According to yet further embodiments, a combination of any 2 or more ofthe above additional lipids is present within the matrix of theinvention. According to certain embodiments, the polymer,phosphatidylcholine, phosphatidylethanolamine, sterol, and additionallipid(s) are all incorporated into the matrix composition. Eachpossibility represents a separate embodiment of the present invention.

According to yet additional embodiments, a composition of the presentinvention further comprises a phosphatidylserine. As used herein,“phosphatidylserine” refers to a phosphoglyceride having aphosphorylserine head group. Phosphatidylserine compounds, in anotherembodiment, have the following structure:

The R and R′ moieties are fatty acids, typically naturally occurringfatty acids or derivatives of naturally occurring fatty acids. Inanother embodiment, the fatty acid moieties are saturated fatty acidmoieties. In another embodiment, the fatty acid moieties have at least14 carbon atoms. In another embodiment, the fatty acid moieties have atleast 16 carbon atoms. In another embodiment, the fatty acid moietiesare chosen such that the gel-to-liquid-crystal transition temperature ofthe resulting matrix is at least 40° C. In another embodiment, the fattyacid moieties are both myristoyl. In another embodiment, the fatty acidmoieties are both palmitoyl. In another embodiment, the fatty acidmoieties are both stearoyl. In another embodiment, the fatty acidmoieties are both arachidoyl. In another embodiment, the fatty acidmoieties are myristoyl and stearoyl. In another embodiment, the fattyacid moieties are a combination of two of the above fatty acid moieties.

In other embodiments, the phosphatidylserine is a naturally-occurringphosphatidyl serine. In another embodiment, the phosphatidylserine is asynthetic phosphatidyl serine. In another embodiment, thephosphatidylserine is a deuterated phosphatidyl serine. In anotherembodiment, the phosphatidylserine contains a naturally-occurringdistribution of isotopes. In another embodiment, the phosphatidylserineis a symmetric phosphatidylserine. In another embodiment, thephosphatidylserine is an asymmetric phosphatidylserine.

Non-limiting examples of phosphatidylserines are phosphatidylserinesmodified with any of the fatty acid moieties enumerated hereinabove. Inanother embodiment, the phosphatidylserine is any otherphosphatidylserine known in the art. Each phosphatidylserine representsa separate embodiment of the present invention.

In other embodiments, a composition of the present invention furthercomprises a phosphatidylglycerol. “Phosphatidylglycerol” as used hereinrefers to a phosphoglyceride having a phosphoryl glycerol head group.Phosphatidylglycerol compounds, in another embodiment, have thefollowing structure:

The 2 bonds to the left are connected to fatty acids, typicallynaturally occurring fatty acids or derivatives of naturally occurringfatty acids. In another embodiment, the phosphatidylglycerol is anaturally-occurring phosphatidylglycerol. In another embodiment, thephosphatidylglycerol is a synthetic phosphatidyl glycerol. In anotherembodiment, the phosphatidylglycerol is a deuteratedphosphatidylglycerol. In another embodiment, the phosphatidylglycerolcontains a naturally-occurring distribution of isotopes. In anotherembodiment, the phosphatidylglycerol is a symmetricphosphatidylglycerol. In another embodiment, the phosphatidylglycerol isan asymmetric phosphatidylglycerol. In another embodiment, the termincludes diphosphatidylglycerol compounds having the followingstructure:

The R and R′ moieties are fatty acids, typically naturally occurringfatty acids or derivatives of naturally occurring fatty acids. Inanother embodiment, the fatty acid moieties are saturated fatty acidmoieties. In another embodiment, the fatty acid moieties have at least14 carbon atoms. In another embodiment, the fatty acid moieties have atleast 16 carbon atoms. In another embodiment, the fatty acid moietiesare chosen such that the gel-to-liquid-crystal transition temperature ofthe resulting matrix is at least 40° C. In another embodiment, the fattyacid moieties are both myristoyl. In another embodiment, the fatty acidmoieties are both palmitoyl. In another embodiment, the fatty acidmoieties are both stearoyl. In another embodiment, the fatty acidmoieties are both arachidoyl. In another embodiment, the fatty acidmoieties are myristoyl and stearoyl. In another embodiment, the fattyacid moieties are a combination of two of the above fatty acid moieties.

Non-limiting examples of phosphatidylglycerols are phosphatidylglycerolsmodified with any of the fatty acid moieties enumerated hereinabove. Inanother embodiment, the phosphatidylglycerol is any otherphosphatidylglycerol known in the art. Each phosphatidylglycerolrepresents a separate embodiment of the present invention.

In yet additional embodiments, a composition of the present inventionfurther comprises a phosphatidylinositol. As used herein, “phosphatidylinositol” refers to a phosphoglyceride having a phosphorylinositol headgroup. Phosphatidylinositol compounds, in another embodiment, have thefollowing structure:

The R and R′ moieties are fatty acids, typically naturally occurringfatty acids or derivatives of naturally occurring fatty acids. Inanother embodiment, the fatty acid moieties are saturated fatty acidmoieties. In another embodiment, the fatty acid moieties have at least14 carbon atoms. In another embodiment, the fatty acid moieties have atleast 16 carbon atoms. In another embodiment, the fatty acid moietiesare chosen such that the gel-to-liquid-crystal transition temperature ofthe resulting matrix is at least 40° C. In another embodiment, the fattyacid moieties are both myristoyl. In another embodiment, the fatty acidmoieties are both palmitoyl. In another embodiment, the fatty acidmoieties are both stearoyl. In another embodiment, the fatty acidmoieties are both arachidoyl. In another embodiment, the fatty acidmoieties are myristoyl and stearoyl. In another embodiment, the fattyacid moieties are a combination of two of the above fatty acid moieties.

In another embodiment, the phosphatidyl inositol is anaturally-occurring phosphatidylinositol. In another embodiment, thephosphatidylinositol is a synthetic phosphatidylinositol. In anotherembodiment, the phosphatidylinositol is a deuteratedphosphatidylinositol. In another embodiment, the phosphatidylinositolcontains a naturally-occurring distribution of isotopes. In anotherembodiment, the phosphatidylinositol is a symmetricphosphatidylinositol. In another embodiment, the phosphatidylinositol isan asymmetric phosphatidylinositol.

Non-limiting examples of phosphatidylinositols are phosphatidylinositolsmodified with any of the fatty acid moieties enumerated hereinabove. Inanother embodiment, the phosphatidylinositol is any otherphosphatidylinositol known in the art. Each phosphatidylinositolrepresents a separate embodiment of the present invention.

In further embodiments, a composition of the present invention furthercomprises a sphingolipid. In certain embodiments, the sphingolipid isceramide. In yet other embodiments, the sphingolipid is a sphingomyelin.“Sphingomyelin” refers to a sphingosine-derived phospholipid.Sphingomyelin compounds, in another embodiment, have the followingstructure:

The R moiety is a fatty acid, typically a naturally occurring fatty acidor a derivative of a naturally occurring fatty acid. In anotherembodiment, the sphingomyelin is a naturally-occurring sphingomyelin. Inanother embodiment, the sphingomyelin is a synthetic sphingomyelin. Inanother embodiment, the sphingomyelin is a deuterated sphingomyelin. Inanother embodiment, the sphingomyelin contains a naturally-occurringdistribution of isotopes.

In another embodiment, the fatty acid moiety of a sphingomyelin ofmethods and compositions of the present invention has at least 14 carbonatoms. In another embodiment, the fatty acid moiety has at least 16carbon atoms. In another embodiment, the fatty acid moiety is chosensuch that the gel-to-liquid-crystal transition temperature of theresulting matrix is at least 40° C.

Non-limiting examples of sphingomyelins are sphingomyelins modified withany of the fatty acid moieties enumerated hereinabove. In anotherembodiment, the sphingomyelin is any other sphingomyelin known in theart. Each sphingomyelin represents a separate embodiment of the presentinvention.

“Ceramide” refers to a compound having the structure:

The 2 bonds to the left are connected to fatty acids, typicallynaturally occurring fatty acids or derivatives of naturally occurringfatty acids. In another embodiment, the fatty acids are longer-chain (toC₂₄ or greater). In another embodiment, the fatty acids are saturatedfatty acids. In another embodiment, the fatty acids are monoenoic fattyacids. In another embodiment, the fatty acids are n-9 monoenoic fattyacids. In another embodiment, the fatty acids contain a hydroxyl groupin position 2. In another embodiment, the fatty acids are other suitablefatty acids known in the art. In another embodiment, the ceramide is anaturally-occurring ceramide. In another embodiment, the ceramide is asynthetic ceramide. In another embodiment, the ceramide is incorporatedinto the matrix composition. Each possibility represents a separateembodiment of the present invention.

Each sphingolipid represents a separate embodiment of the presentinvention.

In certain embodiments, a composition of the present invention furthercomprises a pegylated lipid. In another embodiment, the PEG moiety has aMW of 500-5000 daltons. In another embodiment, the PEG moiety has anyother suitable MW. Non-limiting examples of suitable PEG-modified lipidsinclude PEG moieties with a methoxy end group, e.g. PEG-modifiedphosphatidylethanolamine and phosphatidic acid (structures A and B),PEG-modified diacylglycerols and dialkylglycerols (structures C and D),PEG-modified dialkylamines (structure E) and PEG-modified1,2-diacyloxypropan-3-amines (structure F) as depicted below. In anotherembodiment, the PEG moiety has any other end group used in the art. Inanother embodiment, the pegylated lipid is selected from the groupconsisting of a PEG-modified phosphatidylethanolamine, a PEG-modifiedphosphatidic acid, a PEG-modified diacylglycerol, a PEG-modifieddialkylglycerol, a PEG-modified dialkylamine, and a PEG-modified1,2-diacyloxypropan-3-amine. In another embodiment, the pegylated lipidis any other pegylated phospholipid known in the art. Each possibilityrepresents a separate embodiment of the present invention.

According to certain embodiments, the pegylated lipid is present in anamount of about 50 mole percent of total lipids in the matrixcomposition. In other embodiments, the percentage is about 45 mole %,alternatively about 40 mole %, about 35 mole about 30 mole %, about 25mole %, about 20 mole %, about 15 mole %, about 10 mole %, and about 5mole % or less. Each possibility represents a separate embodiment of thepresent invention.

Polymers

According to certain embodiments, the biocompatible polymer isbiodegradable. According to certain currently typical embodiments, thebiodegradable polymer is polyester.

According to certain embodiments, the biodegradable polyester employedaccording to the teachings of the present invention is PLA (polylacticacid). According to typical embodiments, “PLA” refers topoly(L-lactide), poly(D-lactide), and poly(DL-lactide). A representativestructure of poly(DL-lactide) is depicted below:

In other embodiments, the polymer is PGA (polyglycolic acid). In yetadditional embodiments, the polymer is PLGA (poly(lactic-co-glycolicacid). The PLA contained in the PLGA may be any PLA known in the art,e.g. either enantiomer or a racemic mixture. A representative structureof PLGA is depicted below:

According to certain embodiments, the PLGA comprises a 1:1 lacticacid/glycolic acid ratio. In another embodiment, the ratio is 60:40. Inanother embodiment, the ratio is 70:30. In another embodiment, the ratiois 80:20. In another embodiment, the ratio is 90:10. In anotherembodiment, the ratio is 95:5. In another embodiment, the ratio isanother ratio appropriate for an extended in vivo release profile, asdefined herein. In another embodiment, the ratio is 50:50. In certaintypical embodiments, the ratio is 75:25. The PLGA may be either a randomor block copolymer. The PLGA may be also a block copolymer with otherpolymers such as PEG. Each possibility represents a separate embodimentof the present invention.

In another embodiment, the biodegradable polyester is selected from thegroup consisting of a polycaprolactone, a polyhydroxyalkanoate, apolypropylenefumarate, a polyorthoester, a polyanhydride, and apolyalkylcyanoacrylate, provided that the polyester contains a hydrogenbond acceptor moiety. In another embodiment, the biodegradable polyesteris a block copolymer containing a combination of any two monomersselected from the group consisting of a PLA, PGA, a PLGA,polycaprolactone, a polyhydroxyalkanoate, a polypropylenefumarate, apolyorthoester, a polyanhydride, and a polyalkylcyanoacrylate. Inanother embodiment, the biodegradable polyester is a random copolymercontaining a combination of any two of the monomers listed above. Eachpossibility represents a separate embodiment of the present invention.

The molecular weight (MW) of a biodegradable polyester according to theteachings of the present invention is, in another embodiment, betweenabout 10-150 KDa. In another embodiment, the MW is between about 20-150KDa. In another embodiment, the MW is between about 10-140 KDa. Inanother embodiment, the MW is between about 20-130 KDa. In anotherembodiment, the MW is between about 30-120 KDa. In another embodiment,the MW is between about 45-120 KDa. In another typical embodiment, theMW is between about 60-110 KDa. In another embodiment, a mixture of PLGApolymers of different MW is utilized. In another embodiment, thedifferent polymers both have a MW in one of the above ranges. Eachpossibility represents a separate embodiment of the present invention.

In another embodiment, the biodegradable polymer is selected from thegroup of polyamines consisting of peptides containing one or more typesof amino acids, with at least 10 amino acids.

“Biodegradable,” as used herein, refers to a substance capable of beingdecomposed by natural biological processes at physiological pH.“Physiological pH” refers to the pH of body tissue, typically between6-8. “Physiological pH” does not refer to the highly acidic pH ofgastric juices, which is typically between 1 and 3.

According to some embodiments, the biocompatible polymer isnon-biodegradable polymer. According to certain embodiments, thenon-biodegradable polymer may be selected from the group consisting of,yet not limited to, polyethylene glycol, polyethylene glycol (PEG)acrylate, polymethacrylates (e.g. PEG methacrylate,polymethylmethacrylate, polyethylmethacrylate, polybutylmethacrylate,poly-2-ethylhexylmethacrylate, polylaurylmethacrylate, polyhydroxylethylmethacrylate), poly-methylacrylate,2-methacryloyloxyethylphosphorylcholine (MPC), polystyrene, derivatizedpolystyrene, polylysine, poly N-ethyl-4-vinyl-pyridinium bromide,silicone, ethylene-vinyl acetate copolymers, polyethylenes,polypropylenes, polytetrafluoroethylenes, polyurethanes, polyacrylates,polyvinyl acetate, ethylene vinyl acetate, polyethylene, polyvinylchloride, polyvinyl fluoride, copolymers of polymers of ethylene-vinylacetates and acyl substituted cellulose acetates, poly(vinyl imidazole),chlorosulphonate polyolefins, polyethylene oxide, and mixtures thereof.

Nucleic Acid Agents

The nucleic acid agents or oligonucleotides of the present invention arepreferably no more than about 1000 bases in length, typically no morethan about 100 bases in length. In other typical embodiments, theoligonucleotides are no more than 30 nucleotides (or base pairs) inlength. The nucleic acid agents may be single stranded, double stranded,triple helix, or any combination thereof. In case the nucleic acidagents include more than one strand, the strands do not necessarily needto be 100% complementary.

The terms “oligonucleotide”, “oligonucleic acid” and “polynucleotide”are used interchangeably and refer to an oligomer or polymer ofribonucleic acids (ribo-oligonucleotide or ribo-oligonucleoside) ordeoxyribonucleic acids. These terms include nucleic acid strandscomposed of naturally occurring nucleobases, sugars and covalentinter-sugar linkages as well as oligonucleotides having non-naturallyoccurring portions which function similarly. Such modified orsubstituted oligonucleotides may be preferred over native forms becauseof the valuable characteristics including, for example, increasedstability in the presence of plasma nucleases and enhanced cellularuptake.

According to certain embodiments, the nucleic acids used according tothe teachings of the present invention are antisense molecules. The term“antisense molecule”, “antisense fragment” or “antisense” as used hereinmay refer to any polynucleotide having inhibitory antisense activity,said activity causing a decrease in the expression of the endogenousgenomic copy of the corresponding gene. An antisense molecule is apolynucleotide which comprises consecutive nucleotides having a sequenceof sufficient length and homology to a sequence present within thesequence of the target gene to permit hybridization of the antisensemolecule to the gene. An antisense molecule may inactivate target DNAand/or RNA (such as, for example, mRNA, microRNA, and the like)sequences, and it may be single stranded, double stranded or triplehelix. In case the antisense molecule includes more than one strand, thestrands do not necessarily need to be 100% complementary.

RNA Interference (RNAi)

The term “RNA interference” or “RNAi” refers generally to a process inwhich a double-stranded RNA molecule changes the expression of a nucleicacid sequence with which the double-stranded or short hairpin RNAmolecule shares substantial or total homology. The term “RNAi agent”refers to an RNA sequence that elicits RNAi.

Two types of small RNA molecules—microRNA (miRNA) and small interferingRNA (siRNA)—are central to RNA interference. RNAs are the directproducts of genes, and these small RNAs can bind to specific other RNAsand either increase or decrease their activity, for example bypreventing a messenger RNA from producing a protein. RNA interferencehas an important role in the natural defense of cells against parasiticgenes—viruses and transposons—but also in directing development as wellas gene expression in general.

The term “microRNA” or “miRNA” is used herein in accordance with itsordinary meaning in the art. miRNAs are single-stranded non coding RNAmolecules of about 18-26 nucleotides. miRNAs are processed from primarytranscripts known as pri-miRNA to short stem-loop structures calledpre-miRNA and finally to functional miRNA. Typically, a portion of theprecursor miRNA is cleaved to produce the final miRNA molecule. Thestem-loop structures may range from, for example, about 50 to about 80nucleotides, or about 60 nucleotides to about 70 nucleotides (includingthe miRNA residues, those pairing to the miRNA, and any interveningsegments). Mature miRNA molecules are partially complementary to one ormore messenger RNA (mRNA) molecules, and they function to regulate geneexpression. Examples of miRNAs to be used according to embodiments ofthe present invention include and yet are not limited to miRNA found inthe miRNA database known as miRBase (http://microrna.sanger.ac.uk/).

“Small interfering RNA”, also referred to as “short interfering RNA” or“siRNA”, are short double stranded RNA (“dsRNA”) molecules, which arepresent in the cell. dsRNA cause the destruction of messenger RNAs(“mRNAs”) that share sequence homology with the siRNA to within onenucleotide resolution. It is believed that the siRNA and the targetedmRNA bind to an “RNA-induced silencing complex” or “RISC”, which cleavesthe targeted mRNA. The siRNA is apparently recycled much like amultiple-turnover enzyme, with 1 siRNA molecule capable of inducingcleavage of approximately 1000 mRNA molecules. siRNA-mediated RNAidegradation of an mRNA is therefore more effective than currentlyavailable technologies for inhibiting expression of a target gene.

Typically, an siRNA is a double-stranded nucleic acid moleculecomprising two nucleotide strands. The length of each strand can varysignificantly. The term “length” when referring to a double-strandedinterfering RNA means that the antisense and sense strands independentlyhave a certain length, including interfering RNA molecules where thesense and antisense strands are connected by a linker molecule. siRNAshave a well-defined structure: a short double strand of RNA with2-nucleotides 3′ overhangs on either end.

RNA interference is a two-step process. During the first step, which istermed the initiation step, input dsRNA is digested into 21-23nucleotide (nt) small interfering RNAs (siRNA), probably by the actionof Dicer, a member of the RNase III family of dsRNA-specificribonucleases, which cleaves dsRNA (introduced directly or via anexpressing vector, cassette or virus) in an ATP-dependent manner.

The term “ddRNAi agent” refers to an RNAi agent that is transcribed froma vector. The terms “short hairpin RNA” or “shRNA” refer to an RNAstructure having a duplex region and a loop region.

Although the RNA interference effect, which is mediated by smallinterfering RNA (siRNA) or micro-RNA, has a recognized potentialapplication to human therapy, its application is limited due to the lackof delivery means suitable for human use.

The nucleic acid agents of the present invention can be generatedaccording to any nucleic acid production method known in the art,including both enzymatic syntheses and solid-phase syntheses, as well asusing recombinant methods well known in the art.

Equipment and reagents for executing solid-phase synthesis arecommercially available from, for example, Applied Biosystems. Any othermeans for such synthesis may also be employed; the actual synthesis ofthe nucleic acid agents is well within the capabilities of one skilledin the art and can be accomplished via established methodologies asdetailed in, for example: Sambrook, J. and Russell, D. W. (2001),“Molecular Cloning: A Laboratory Manual”; Ausubel, R. M. et al., eds.(1994, 1989), “Current Protocols in Molecular Biology,” Volumes I-III,John Wiley & Sons, Baltimore, Md.; Perbal, B. (1988), “A Practical Guideto Molecular Cloning,” John Wiley & Sons, New York.

It will be appreciated that nucleic acid agents of the present inventioncan be also generated using an expression vector as is further describedhereinbelow.

Optionally, the nucleic acid agents of the present invention aremodified. Nucleic acid agents can be modified using various methodsknown in the art.

In certain embodiments, the nucleic acid agents are modified either inbackbone, internucleoside linkages, or bases, as is known in the art andas described herebelow.

Specific examples of nucleic acid agents useful according to theseembodiments of the present invention include oligonucleotides orpolynucleotides containing modified backbones or non-naturalinternucleoside linkages. Examples of oligonucleotides orpolynucleotides having modified backbones include those that retain aphosphorus atom in the backbone. Other modified oligonucleotidebackbones include, for example: phosphorothioates; chiralphosphorothioates; phosphorodithioates; phosphotriesters; aminoalkylphosphotriesters; methyl and other alkyl phosphonates, including3′-alkylene phosphonates and chiral phosphonates; phosphinates;phosphoramidates, including 3′-amino phosphoramidate andaminoalkylphosphoramidates; thionophosphoramidates;thionoalkylphosphonates; thionoalkylphosphotriesters; andboranophosphates having normal 3′-5′ linkages, 2′-5′ linked analogs ofthese, and those having inverted polarity wherein the adjacent pairs ofnucleoside units are linked 3′-5′ to 5′-3′ or 2′-5′ to 5′-2′. Varioussalts, mixed salts, and free acid forms of the above modifications canalso be used.

Alternatively, modified oligonucleotide backbones that do not include aphosphorus atom therein have backbones that are formed by short-chainalkyl or cycloalkyl internucleoside linkages, mixed heteroatom and alkylor cycloalkyl internucleoside linkages, or one or more short-chainheteroatomic or heterocyclic internucleoside linkages. These includethose having morpholino linkages (formed in part from the sugar portionof a nucleoside); siloxane backbones; sulfide, sulfoxide, and sulfonebackbones; formacetyl and thioformacetyl backbones; methylene formacetyland thioformacetyl backbones; alkene-containing backbones; sulfamatebackbones; methyleneimino and methylenehydrazino backbones; sulfonateand sulfonamide backbones; amide backbones; and others having mixed N,O, S and CH₂ component parts.

Other non-limiting examples of oligonucleotides or polynucleotidescontemplated by the present invention include nucleic acid analogscontaining bicyclic and tricyclic nucleoside and nucleotide analogsreferred to as “locked nucleic acids,” “locked nucleoside analogues,” or“LNAs” (see, e.g., U.S. Pat. No. 6,083,482).

Other nucleic acid agents that may be used according to the presentinvention are those modified in both sugar and the internucleosidelinkage, i.e., the backbone of the nucleotide units is replaced withnovel groups. The base units are maintained for complementation with theappropriate polynucleotide target. Nucleic acid agents of the presentinvention may also include base modifications or substitutions. As usedherein, “unmodified” or “natural” bases include the purine bases adenine(A) and guanine (G) and the pyrimidine bases thymine (T), cytosine (C),and uracil (U). “Modified” bases include but are not limited to othersynthetic and natural bases, such as: 5-methylcytosine (5-me-C);5-hydroxymethyl cytosine; xanthine; hypoxanthine; 2-aminoadenine;6-methyl and other alkyl derivatives of adenine and guanine; 2-propyland other alkyl derivatives of adenine and guanine; 2-thiouracil,2-thiothymine, and 2-thiocytosine; 5-halouracil and cytosine; 5-propynyluracil and cytosine; 6-azo uracil, cytosine, and thymine; 5-uracil(pseudouracil); 4-thiouracil; 8-halo, 8-amino, 8-thiol, 8-thioalkyl,8-hydroxyl, and other 8-substituted adenines and guanines; 5-halo,particularly 5-bromo, 5-trifluoromethyl, and other 5-substituted uracilsand cytosines; 7-methylguanine and 7-methyladenine; 8-azaguanine and8-azaadenine; 7-deazaguanine and 7-deazaadenine; and 3-deazaguanine and3-deazaadenine.

The nucleic acid-based agents of the present invention may be producedusing standard recombinant and synthetic methods well known in the art.An isolated nucleic acid sequence can be obtained from its naturalsource, either as an entire (i.e., complete) gene or a portion thereof.A nucleic acid molecule can also be produced using recombinant DNAtechnology (e.g., polymerase chain reaction (PCR) amplification,cloning) or chemical synthesis. Nucleic acid sequences include naturalnucleic acid sequences and homologs thereof, including, but not limitedto, natural allelic variants and modified nucleic acid sequences inwhich nucleotides have been inserted, deleted, substituted, and/orinverted in such a manner that such modifications do not substantiallyinterfere with the function of the nucleic acid molecules.

A nucleic acid molecule homolog can be produced using a number ofmethods known to those skilled in the art. For example, nucleic acidmolecules can be modified using a variety of techniques including, butnot limited to, classic mutagenesis techniques and recombinant DNAtechniques, such as site-directed mutagenesis, chemical treatment of anucleic acid molecule to induce mutations, restriction enzyme cleavageof a nucleic acid fragment, ligation of nucleic acid fragments,polymerase chain reaction (PCR) amplification and/or mutagenesis ofselected regions of a nucleic acid sequence, synthesis ofoligonucleotide mixtures and ligation of mixture groups to “build” amixture of nucleic acid molecules and combinations thereof.

Polyethylene Glycol

The present invention is based in part on the unexpected discovery thatincubation of an aqueous solution comprising polynucelotides withpolyethylene glycol (PEG) enhances the capture of the polynucleotidewithin the lipid-based matrix and affects the release rate of thepolynucelotides from the matrix under suitable conditions. As commonlyused in the art, poly(ethylene)glycol generally refers to the linearform of poly(ethylene glycol) since these are the most common,commercially available PEG. Linear PEG can be represented by the formulaOH—(CH₂CH₂O)_(n)—OH (diol) or mPEG, CH₃O—(CH₂CH₂O)_(n)OH, wherein n isthe average number of repeating ethylene oxide groups. These PEGcompounds are commercially available from, e.g., Sigma-Aldrich in avariety of molecular weights ranging from 1000 to 300,000. Linear PEGsare available as monofunctional or bifunctional forms. PEG's may containfunctional reactive groups at either end of the chain and can behomobifunctional (two identical reactive groups) or heterobifunctional(two different reactive groups). For example, heterobifunctional PEG ofthe formula _(NH2)—(CH₂CH₂O)_(n)COOH are commercially available and areuseful for forming PEG derivatives. There are many grades of PEGcompounds that are represented by theirs average molecular weight.Pharmaceutical grade PEG is typically in a molecular range of up to5,000. According to certain typical embodiments, the PEG used accordingto the teachings of the present invention has a molecular weight of upto 1,000, typically about 2,000-5000.

Additional Components

The matrix composition of the present invention optionally furthercomprises a free fatty acid. In certain embodiments, the free fatty acidis an omega-6 fatty acid. In other embodiments, the free fatty acid isan omega-9 fatty acid. In another embodiment, the free fatty acid isselected from the group consisting of omega-6 and omega-9 fatty acids.In further embodiments, the free fatty acid has 14 or more carbon atoms.In another embodiment, the free fatty acid has 16 or more carbon atoms.In another embodiment, the free fatty acid has 16 carbon atoms. Inanother embodiment, the free fatty acid has 18 carbon atoms. In anotherembodiment, the free fatty acid has 16-22 carbon atoms. In anotherembodiment, the free fatty acid has 16-20 carbon atoms. In anotherembodiment, the free fatty acid has 16-18 carbon atoms. In anotherembodiment, the free fatty acid has 18-22 carbon atoms. In anotherembodiment, the free fatty acid has 18-20 carbon atoms. In anotherembodiment, the free fatty acid is linoleic acid. In another embodiment,the free fatty acid is linolenic acid. In another embodiment, the freefatty acid is oleic acid. In another embodiment, the free fatty acid isselected from the group consisting of linoleic acid, linolenic acid, andoleic acid. In another embodiment, the free fatty acid is anotherappropriate free fatty acid known in the art. In another embodiment, thefree fatty acid adds flexibility to the matrix composition. In anotherembodiment, the free fatty acid slows the release rate, including the invivo release rate. In another embodiment, the free fatty acid improvesthe consistency of the controlled release, particularly in vivo. Inanother embodiment, the free fatty acid is saturated. In anotherembodiment, incorporation of a saturated fatty acid having at least 14carbon atoms increases the gel-fluid transition temperature of theresulting matrix composition.

In another embodiment, the free fatty acid is incorporated into thematrix composition.

In another embodiment, the free fatty acid is deuterated. In anotherembodiment, deuteration of the lipid acyl chains lowers the gel-fluidtransition temperature.

Each type of fatty acid represents a separate embodiment of the presentinvention.

According to certain embodiments, a matrix composition of the presentinvention further comprises a tocopherol. The tocopherol is, in anotherembodiment, E307 (α-tocopherol). In another embodiment, the tocopherolis β-tocopherol. In another embodiment, the tocopherol is E308(γ-tocopherol). In another embodiment, the tocopherol is E309(δ-tocopherol). In another embodiment, the tocopherol is selected fromthe group consisting of α-tocopherol, β-tocopherol, γ-tocopherol, andδ-tocopherol. In another embodiment, the tocopherol is incorporated intothe matrix composition. Each possibility represents a separateembodiment of the present invention.

The matrix composition of the present invention optionally furthercomprises physiologically acceptable buffer salts, which are well knownin the art. Non-limiting examples of physiologically acceptable buffersalts are phosphate buffers. A typical example of a phosphate buffer is40 parts NaCl, 1 part KCl, 7 parts Na₂HPO₄.2H₂O and 1 part KH₂PO₄. Inanother embodiment, the buffer salt is any other physiologicallyacceptable buffer salt known in the art. Each possibility represents aseparate embodiment of the present invention.

Release Rates and General Characteristics of the Matrix Compositions

The release time of 90% of the active ingredient for matrix compositionsof the present invention under suitable conditions is preferably between4 days and 6 months. In another embodiment, the release time is between1 week and 6 months. In another embodiment, the release time is between1 week and 5 months. In another embodiment, the release time is between1 week and 5 months. In another embodiment, the release time is between1 week and 4 months. In another embodiment, the release time is between1 week and 3 months. In another embodiment, the release time is between1 week and 2 months. In another embodiment, the release time is between2 weeks and 6 months. In another embodiment, the release time is between2 weeks and 5 months. In another embodiment, the release time is between2 weeks and 4 months. In another embodiment, the release time is between2 weeks and 3 months. In another embodiment, the release time is between3 weeks and 6 months. In another embodiment, the release time is between3 weeks and 5 months. In another embodiment, the release time is between3 weeks and 4 months. In another embodiment, the release time is between3 weeks and 3 months. Each possibility represents a separate embodimentof the present invention.

The sustained release period using the compositions of the presentinvention can be programmed taking into account four major factors: (i)the weight ratio between the polymer and the lipid content, specificallythe phospholipid having fatty acid moieties of at least 14 carbons, (ii)the biochemical and/or biophysical properties of the biopolymers and thelipids used; (iii) the ratio between the different lipids used in agiven composition and (iv) the incubation time of the nucleic acid agentwith polyethylene glycol.

As exemplified herein below, when the matrix is devoid of the lipidportion most of the loaded polynucleotide is released within the firsthour, indicating that the lipid mass is essential for graduate releaseof the polynucleotides. The ratio of total lipids to the polymer inorder to achieve lipid saturation can be determined by a number ofmethods, as described herein. According to certain embodiments, thelipid:polymer weight ratio of a composition of the present invention isbetween 1:1 and 9:1 inclusive. In another embodiment, the ratio isbetween 1.5:1 and 9:1 inclusive. In another embodiment, the ratio isbetween 2:1 and 9:1 inclusive. In another embodiment, the ratio isbetween 3:1 and 9:1 inclusive. In another embodiment, the ratio isbetween 4:1 and 9:1 inclusive. In another embodiment, the ratio isbetween 5:1 and 9:1 inclusive. In another embodiment, the ratio isbetween 6:1 and 9:1 inclusive. In another embodiment, the ratio isbetween 7:1 and 9:1 inclusive. In another embodiment, the ratio isbetween 8:1 and 9:1 inclusive. In another embodiment, the ratio isbetween 1.5:1 and 5:1 inclusive. Each possibility represents a separateembodiment of the present invention.

In another embodiment for purposes of illustration, in the case whereinthe polymer is predominantly 40 KDa PLGA (poly(lactic-co-glycolic acid,1:1 ratio)), the molar ratio of total lipids to 40 KDa PLGA is typicallyin the range of 20-100 inclusive. In another embodiment, the molar ratioof total lipids to 40 KDa PLGA is between 20-200 inclusive. In anotherembodiment, the molar ratio is between 10-100 inclusive. In anotherembodiment, the molar ratio is between 10-200 inclusive. In anotherembodiment, the molar ratio is between 10-50 inclusive. In anotherembodiment, the molar ratio is between 20-50 inclusive. Each possibilityrepresents a separate embodiment of the present invention.

Implants and Other Pharmaceutical Compositions

The matrix composition of the present invention can be molded to theform of an implant, following removal of the organic solvents and water.The removal of the solvents is typically performed by evaporation undera specific temperature between room temperature and 90° C., followed byvacuum.

In another embodiment, the implant is homogeneous. In anotherembodiment, the implant is manufactured by a process comprising the stepof freeze-drying the material in a mold. Each possibility represents aseparate embodiment of the present invention.

According to additional embodiments, the present invention provides animplant comprising a matrix composition comprising a nucleic acid basedagent of the present invention.

The present invention further provides a process of creating an implantfrom a composition of the present invention comprising the steps of (a)creating a matrix composition according to the method of the presentinvention in the form of a bulk material; (b) transferring the bulkmaterial into a mold or solid receptacle of a desired shaped; (c)freezing the bulk material; and (d) lyophilizing the bulk material.

In additional embodiments, the present invention provides apharmaceutical composition comprising a matrix composition of thepresent invention. According to certain embodiments, the pharmaceuticalcomposition further comprises additional pharmaceutically acceptableexcipients. In additional embodiments, the pharmaceutical composition isin a parenterally injectable form. In other embodiments, thepharmaceutical composition is in an infusible form. In yet additionalembodiments, the excipient is compatible for injection. In furtherembodiments, the excipient is compatible for infusion. Each possibilityrepresents a separate embodiment of the present invention.

Use of the matrix composition of the present invention for theproduction of micro-vesicles, ranging from 100 nm to 50 m is also withinthe scope of the present invention.

According to certain embodiments, the matrix composition of the presentinvention is in the form of microspheres, following removal of theorganic solvents and water. In other embodiment, the microspheres arehomogeneous. According to certain embodiments, the microspheres aremanufactured by a process comprising the step of spray-drying. Eachpossibility represents a separate embodiment of the present invention.

In another embodiment, the present invention provides microspheres madeof a matrix composition of the present invention. In another embodiment,the present invention provides a pharmaceutical composition comprisingmicrospheres of the present invention and a pharmaceutically acceptableexcipient. Each possibility represents a separate embodiment of thepresent invention.

In another embodiment, the particle size of microspheres of the presentinvention is approximately 500-2000 nm. In another embodiment, theparticle size is about 400-2500 nm. In another embodiment, the particlesize is about 600-1900 nm. In another embodiment, the particle size isabout 700-1800 nm. In another embodiment, the particle size is about500-1800 nm. In another embodiment, the particle size is about 500-1600nm. In another embodiment, the particle size is about 600-2000 nm. Inanother embodiment, the particle size is about 700-2000 nm. In anotherembodiment, the particles are of any other size suitable forpharmaceutical administration. Each possibility represents a separateembodiment of the present invention.

Methods of Making Matrix Compositions of the Present Invention

The present invention further provides a process for producing a matrixcomposition for sustained release of a nucleic acid agent comprising:

(a) mixing into a first volatile organic solvent (i) a biodegradablepolymer and (ii) a first lipid component comprising at least one lipidhaving a polar group;

(b) mixing polyethylene glycol into a water-based solution of thenucleic acid agent;

(c) mixing the solution obtained in step (b) with a second volatileorganic solvent and a second lipid component comprising at least onephospholipid having fatty acid moieties of at least 14 carbons;

(d) mixing the solutions obtained in steps (a) and (c) to form ahomogeneous mixture; and

(e) removing the volatile solvents and water,

Thereby producing a homogeneous polymer-phospholipids matrix comprisingthe nucleic acid agent.

According to certain typical embodiments, the method comprises the stepsof (a) mixing into a first volatile organic solvent: (i) a biodegradablepolyester and (ii) sterol; (b) mixing into a different containercontaining nucleic acid based drug in water-based solution comprisingpolyethylene glycol (1) a phosphatidylcholine in a second water-misciblevolatile organic solvent and/or (2) a phosphatidylethanolamine in thewater-miscible volatile organic solvent and (3) mixing the resultingsolution in a given temperature (4) optionally precipitating theresulting material by centrifugation or by freeze-drying and optionallyre-suspending the precipitate in a selected volatile solvent; and (c)mixing and homogenizing the products resulting from steps (a) and (b).

According to certain embodiments, the biodegradable polymer is selectedfrom the group consisting of PLGA, PGA PLA or combinations thereof. Inother embodiments, the biodegradable polyester is any other suitablebiodegradable polyester known in the art. According to yet additionalembodiments, the biodegradable polymer is a polyamine. Mixing thepolymer with the at least one lipid having a polar group (non-limitingexample being sterol, particularly cholesterol), within the firstorganic solvent, is typically performed at room temperature. Optionally,α- and/or γ-tocopherol are added to the solution. A lipid-polymer matrixis formed.

The water-based solution containing the at least one nucleic-acid basedagent and polyethylene glycol is mixed, typically under stirring, withthe second volatile organic solvent (selected from the group consistingof, but not limited to N-methylpyrrolidone, ethanol, methanol, ethylacetate or combination thereof) comprising the at least onephospholipid. According to certain embodiments, the phospholipid isphosphocholine or phosphatidylcholine or derivatives thereof. Accordingto other embodiments, the phospholipid is phosphatidylcholine or aderivative thereof. According to additional embodiments, the secondvolatile organic solvent comprises combination of phosphatidylcholine,phosphatidylcholine or derivatives thereof. According to certainembodiments, the phosphocholine or phosphatidylcholine or derivativesthereof is present at 10-90% mass of all lipids in the matrix, i.e.10-90 mass % of phospholipids, sterols, ceramides, fatty acids etc.According to other embodiments, the phosphatidylethanolamine is presentas 10-90 mass % of all lipids in the matrix.

According to yet other embodiments, phosphocholine orphosphatidylcholine derivative or their combination at different ratioswith phosphatidylethanolamine are mixed in the organic solvent prior toits addition to the water based solution comprising the nucleic acidsand PEG.

In another embodiment, the phosphatidylethanolamine is also included inthe first lipid component.

In another embodiment, the mixture (a) containing the organic solvent ishomogenized prior to mixing it with the mixture containing thewater-miscible organic solvent. In another embodiment, the mixture (c)containing the water-miscible organic solvent is homogenized prior tomixing it with the mixture containing another type of organic solvent.In another embodiment, the polymer in the mixture of step (a) is lipidsaturated. In another embodiment, the matrix composition is lipidsaturated. Typically, the polymer and the phosphatidylcholine areincorporated into the matrix composition. In another embodiment, theactive agent as well is incorporated into the matrix composition. Inanother embodiment, the matrix composition is in the form of alipid-saturated matrix whose shape and boundaries are determined by thebiodegradable polymer. Each possibility represents a separate embodimentof the present invention.

In another embodiment, the phosphatidylethanolamine has saturated fattyacid moieties. In another embodiment, the fatty acid moieties have atleast 14 carbon atoms. In another embodiment, the fatty acid moietieshave 14-18 carbon atoms. Each possibility represents a separateembodiment of the present invention.

In another embodiment, the phosphatidylcholine has saturated fatty acidmoieties. In another embodiment, the fatty acid moieties have at least14 carbon atoms. In another embodiment, the fatty acid moieties have atleast 16 carbon atoms. In another embodiment, the fatty acid moietieshave 14-18 carbon atoms. In another embodiment, the fatty acid moietieshave 16-18 carbon atoms. Each possibility represents a separateembodiment of the present invention.

In another embodiment, the molar ratio of total lipids to polymer in thenon-polar organic solvent is such that the polymer in this mixture islipid-saturated. In another embodiment for purposes of illustration, inthe case wherein the polymer is predominantly 50 KDa PLGA(poly(lactic-co-glycolic acid, 1:1 ratio)), the molar ratio of totallipids to 50 KDa PLGA is typically in the range of 10-50 inclusive. Inanother embodiment, the molar ratio of total lipids to 50 KDa PLGA isbetween 10-100 inclusive. In another embodiment, the molar ratio isbetween 20-200 inclusive. In another embodiment, the molar ratio isbetween 20-300 inclusive. In another embodiment, the molar ratio isbetween 30-400 inclusive. Each possibility represents a separateembodiment of the present invention.

Each of the components of the above method and other methods of thepresent invention is defined in the same manner as the correspondingcomponent of the matrix compositions of the present invention.

In another embodiment, step (a) of the production method furthercomprises adding to the volatile organic solvent, typically non-polarsolvent, a phosphatidylethanolamine. In another embodiment, thephosphatidylethanolamine is the same phosphatidylethanolamine includedin step (c). In another embodiment, the phosphatidylethanolamine is adifferent phosphatidylethanolamine that may be any otherphosphatidylethanolamine known in the art. In another embodiment, thephosphatidylethanolamine is selected from the group consisting of thephosphatidylethanolamine of step (c) and a differentphosphatidylethanolamine. Each possibility represents a separateembodiment of the present invention.

In another embodiment, step (c) of the production method furthercomprises adding to the volatile organic solvent, typically awater-miscible solvent, a phospholipid selected from the groupconsisting of a phosphatidylserine, a phosphatidylglycerol, asphingomyelin, and a phosphatidylinositol.

In another embodiment, step (c) of the production method furthercomprises adding to the water-miscible volatile organic solvent asphingolipid. In another embodiment, the sphingolipid is ceramide. Inanother embodiment, the sphingolipid is a sphingomyelin. In anotherembodiment, the sphingolipid is any other sphingolipid known in the art.Each possibility represents a separate embodiment of the presentinvention.

In another embodiment, step (c) of the production method furthercomprises adding to the water-miscible, volatile organic solvent anomega-6 or omega-9 free fatty acid. In another embodiment, the freefatty acid has 16 or more carbon atoms. Each possibility represents aseparate embodiment of the present invention.

Upon mixing, a homogenous mixture is formed, since the polymer islipid-saturated in the mixture of step (a). In another embodiment, thehomogenous mixture takes the form of a homogenous liquid. In anotherembodiment, upon freeze-drying or spray-drying the mixture, vesicles areformed. Each possibility represents a separate embodiment of the presentinvention.

In another embodiment, the production method further comprises the stepof removing the solvent and water present in the product of step (d). Incertain embodiments, the solvent and eater removal utilizes atomizationof the mixture. In other embodiments, the mixture is atomized into dry,heated air. Typically, atomization into heated air evaporates all waterimmediately, obviating the need for a subsequent drying step. In anotherembodiment, the mixture is atomized into a water-free solvent. Inanother embodiment, the liquid removal is performed by spray drying. Inanother embodiment, the liquid removal is performed by freeze drying. Inanother embodiment, the liquid removal is performed using liquidnitrogen. In another embodiment, the liquid removal is performed usingliquid nitrogen that has been pre-mixed with ethanol. In anotherembodiment, the liquid removal is performed using another suitabletechnique known in the art. Each possibility represents a separateembodiment of the present invention.

In another embodiment, a method of the present invention furthercomprises the step of vacuum-drying the composition. In anotherembodiment, the step of vacuum-drying is performed following the step ofevaporation. Each possibility represents a separate embodiment of thepresent invention.

In another embodiment, a method of the present invention furthercomprises the step of evaporating the organic volatile solvent byheating the product of step (d). The heating is continuing until thesolvent is eliminated and in a typical temperature between roomtemperature to 90° C. In another embodiment a step of vacuum-drying isperformed following the step of evaporating. Each possibility representsa separate embodiment of the present invention.

Lipid Saturation and Techniques for Determining Same

“Lipid saturated,” as used herein, refers to saturation of the polymerof the matrix composition with phospholipids in combination with anucleic acid agent and optionally targeting moiety present in thematrix, and any other lipids that may be present. As described herein,matrix compositions of the present invention comprise, in someembodiments, phospholipids other than phosphatidylcholine. In otherembodiments, the matrix compositions may comprise lipids other thanphospholipids. The matrix composition is saturated by whatever lipidsare present. “Saturation” refers to a state wherein the matrix containsthe maximum amount of lipids of the type utilized that can beincorporated into the matrix. Methods for determining the polymer:lipidratio to attain lipid saturation and methods of determining the degreeof lipid saturation of a matrix are known to a person skilled in theart. Each possibility represents a separate embodiment of the presentinvention.

According to certain typical embodiments, the final matrix compositionof the present invention is substantially free of water in contrast tohitherto known lipid-based matrices designed for nucleic acids delivery.In other words, even when the active ingredients are initially dissolvedin an aqueous solution all the solvents are removed during the processof preparing the lipid polymer compositions. The substantially absenceof water from the final composition protects the bioactive nucleic acidfrom degradation or chemical modification, particularly from enzymedegradation. Upon application of the composition to an hydrousbiological environment, the outer surface of the matrix compositioncontacts the biological liquids while the substantially water free innerpart protects the remaining active ingredient thus enabling sustainedrelease of undamaged active ingredient.

According to certain embodiments, the term “substantially free of water”refers to a composition containing less than 1% water by weight. Inanother embodiment, the term refers to a composition containing lessthan 0.8% water by weight. In another embodiment, the term refers to acomposition containing less than 0.6% water by weight. In anotherembodiment, the term refers to a composition containing less than 0.4%water by weight. In another embodiment, the term refers to a compositioncontaining less than 0.2% water by weight. In another embodiment, theterm refers to the absence of amounts of water that affect thewater-resistant properties of the matrix.

In another embodiment, the matrix composition is essentially free ofwater. “Essentially free” refers to a composition comprising less than0.1% water by weight. In another embodiment, the term refers to acomposition comprising less than 0.08% water by weight. In anotherembodiment, the term refers to a composition comprising less than 0.06%water by weight. In another embodiment, the term refers to a compositioncomprising less than 0.04% water by weight. In another embodiment, theterm refers to a composition comprising less than 0.02% water by weight.In another embodiment, the term refers to a composition comprising lessthan 0.01% water by weight. Each possibility represents a separateembodiment of the present invention.

In another embodiment, the matrix composition is free of water. Inanother embodiment, the term refers to a composition not containingdetectable amounts of water. Each possibility represents a separateembodiment of the present invention.

The process of preparing the matrix of the present invention comprisesonly one step where an aqueous solution is used. This solution is mixedwith organic volatile solvent, and all the liquids are removedthereafter. The process of the present invention thus enables lipidsaturation. Lipid saturation confers upon the matrix composition abilityto resist bulk degradation in vivo; thus, the matrix compositionexhibits the ability to mediate extended release on a scale of severalweeks or months.

In another embodiment, the matrix composition is dry. “Dry” refers, inanother embodiment, to the absence of detectable amounts of water ororganic solvent.

In another embodiment, the water permeability of the matrix compositionhas been minimized “Minimizing” the water permeability refers to aprocess of producing the matrix composition mainly in organic solvents,as described herein, in the presence of the amount of lipid that hasbeen determined to minimize the permeability to penetration of addedwater. The amount of lipid required can be determined by hydrating thevesicles with a solution containing tritium-tagged water, as describedherein.

In another embodiment, “lipid saturation” refers to filling of internalgaps (free volume) within the lipid matrix as defined by the externalborder of the polymeric backbone. The gaps are filled with thephospholipids in combination with any other types of lipids, nucleicacid agent and optionally targeting moiety present in the matrix, to theextent that additional lipid moieties can no longer be incorporated intothe matrix to an appreciable extent.

Zero-order release rate” or “zero order release kinetics” means aconstant, linear, continuous, sustained and controlled release rate ofthe nucleic acid agent from the polymer matrix, i.e. the plot of amountsof the nucleic acid agent released vs. time is linear.

Therapeutic Applications of Nucleic Acid Agents

The present invention also relates to a variety of applications in whichit is desired to modulate, e.g., one or more target genes, viralreplication of a pathogenic virus, etc., in a whole eukaryotic organism,e.g., a mammal or a plant; or portion thereof, e.g., tissue, organ,cell, etc. In such methods, an effective amount of a nucleic acid activeagent is administered to the host or introduced into the target cell.The term “effective amount” refers to a dosage sufficient to modulateexpression of the target viral gene(s), as desired, e.g., to achieve thedesired inhibition of viral replication. As indicated above, in certainembodiments of this type of application, the subject methods areemployed to reduce expression of one or more target genes in the host inorder to achieve a desired therapeutic outcome.

When the target gene is a viral gene, e.g., when inhibition of viralreplication is desired, the target viral gene can be from a number ofdifferent viruses. Representative viruses include, but are not limitedto: HBV, HCV, HIV, influenza A, Hepatitis A, picornaviruses,alpha-viruses, herpes viruses, and the like.

The methods described herein are also suitable for inhibiting theexpression of a target gene in a tumor cell. The present inventionrelates to any type of cancer including solid tumors and non-solidtumors. The solid tumors are exemplified by, but are mot limited to, CNStumors, liver cancer, colorectal carcinoma, breast cancer, gastriccancer, pancreatic cancer, bladder carcinoma, cervical carcinoma, headand neck tumors, vulvar cancer and dermatological neoplasms includingmelanoma, squamous cell carcinoma and basal cell carcinomas. Non-solidtumors include lymphoproliferative disorders including leukemias andlymphomas. Each possibility represents a separate embodiment of thepresent invention.

Another application in which the subject methods find use is theelucidation of gene function by a functional analysis of eukaryoticcells, or eukaryotic non-human organisms, preferably mammalian cells ororganisms and most preferably human cells, e.g. cell lines such as HeLaor 293, or rodents, e.g. rats and mice. By transfection with vectormolecules which are homologous to a predetermined target gene encoding asuitable RNA molecule, a specific knockdown phenotype can be obtained ina target cell, e.g. in cell culture or in a target organism.

The present invention is also useful to produce plants with improvedcharacteristics including but not limited to decreased susceptibility tobiotic as well as abiotic stress, insect infestation, pathogeninfection, and improved agricultural characteristics including ripeningcharacteristics. Any gene or genes that may be detrimental in theagricultural community could be a potential target or targets of suchspecially selected nucleic acids.

EXAMPLES Example 1 Platform Technology for Production of Drug CarrierCompositions for the Delivery of Nucleic Acid Based Agents

I. Preparation of First Solution

A Polymer (for example, PLGA, PGA, PLA, or a combination thereof) and asterol (e.g. cholesterol) and/or alpha- or gamma tocopherol are mixed ina volatile organic solvent (e.g. ethyl acetate with/without chloroform).The entire process is performed at room temperature. A lipid-polymermatrix is thus obtained.

II. Preparation of Second Solution

At least one nucleic-based agent is dissolved in water and polyethyleneglycol (PEG) 1,000-8000, typically PEG 5,000 is added. The resultingsolution is mixed, typically under stirring, with a volatile organicsolvent (typically N-methylpyrrolidone, ethanol, methanol, ethyl acetateor combination thereof) comprising:

A phosphocholine or phosphatidylcholine derivative, e.g. deuterated1,2-distearoyl-sn-glycero-3-phosphocholine (DSPC) ordioleoyl-phosphatidylcholine (DOPC), Dipalmitoyl-phosphatidylcholine(DPPC), Dimyristoyl-phosphatidylcholine (DMPC),dioleoyl-phosphatidylcholine (DOPC),1-palmitoyl-2-oleoyl-phosphatidylcholine, present as 10-90 mass % of alllipids in the matrix, i.e. 10-90 mass % of phospholipids, sterols,ceramides, fatty acids etc;

Optionally, phosphatidylethanolamine—e.g. dimethyldimyristoylphosphatidylethanolamine (DMPE) or dipalmitoyl-phosphatidylethanolamine(DPPE)—present as 10-90 mass % of all lipids in the matrix;

Optionally, phosphocholine or phosphatidylcholine derivative or theircombination at different ratios of phosphatidylethanolamine, mixed inthe organic solvent prior to its addition of the NA drug water basedsolution;

Optionally, cationic lipid is included as 0.1-10 mol % of all lipids inthe matrix;

Optionally, 0.1-15 mass % of a free fatty acid, e.g. linoleic acid (LN),or oleic acid (OA), as 0.1-10 mass % of all lipids in the matrix;

The mixture is homogenized, sonicated or used for coating the surface ofmedical devices. Typically the entire process is conducted at roomtemperature, but higher temperatures of up to about 90° C. can be used,typically when highly saturated lipids are used.

III. Mixing the Polymer with the Nucleic Acids-PEG Mixture

The second suspension (or solution) is added to the first solution understirring. Stirring is continued for up to about 5 h. The entire processis performed at room temperature and up to 90° C., all according to thespecific formulation, the nature of the lipids in use and the specificnucleic acid agent. The resulting mixture should be homogenous, but canalso be slightly turbid.

IV. Removal of the Solvents

When coating of surfaces is performed; the suspension from stage III ismixed with the particles or devices to be coated followed by evaporationof the volatile organic solvents. The entire coating process isperformed at a temperature of about 30-90° C.

The solution from stage III may be optionally atomized into dry, heatedair.

Alternatively the solution from stage III is atomized into water basedsolution, which may contain carbohydrates, or atomized into ethanolcovered by liquid nitrogen or only liquid nitrogen without ethanol,after which the nitrogen and/or ethanol (as above) are evaporated.

V. Vacuum Drying

The matrix composition, coated particles and coated devices arevacuum-dried. All organic solvent and water residues are removed. Thelipid-based matrix comprising the nucleic acid agent is ready forstorage.

Example 2 Preparation of a Matrix Comprising Nucleic Acids without PEG

Matrix Preparation

Stock Solutions:

Stock solution 1 (SS1): PLGA 75/25, 300 mg/ml in ethyl acetate (EA).

Stock solution 2 (SS2): Cholesterol (CH), 30 mg/ml in EA.

Stock solution 3 (SS3): DPPC, 300 mg/ml in Methanol:EA (3:1 v/v).

Single strand DNA oligonucleotides (ssDNA) (23 mer, having the sequenceCCATCAACGACCCCTTCATGGAC (SEQ ID NO:1) marked with FAM (fluorescencetagging probe) at the 5′ end, 0.5 mM in DDW.

Solution A was obtained by mixing 0.2 volume of SS1 with 1 volume of SS2(PLGA 50 mg/ml, CH 25 mg/ml).

Solution B was obtained by mixing SS3 and SS4 at 1:1 volume to volumeratio by vortex.

Solution AB was obtained by mixing 1 volume of solution B with 1.5volumes of solution A by vortex and incubating the mixture at 45° C. for5 minutes.

To one volume of the AB solution one volume of MetOH:DDW (v/v) wasadded, followed by vortex and incubation at 45° C. for 10 min (thesolution became uniform and milky).

Coating

100 mg of commercial artificial bone substitute (tricalcium phosphateparticles, TCP) were coated with 0.25 ml of the matrix solution(solution AB).

The solvents were evaporated by incubation at 45° C. for 1 h of until noliquid is visualized, followed by overnight vacuum.

Example 3 Release of ssDNA from the Matrix Composition Prepared withoutPEG

TCP particles coated with the matrix comprising the FAM-labeled ssDNAprepared as described in example 2 hereinabove were hydrated with waterand incubated at 37° C. After 1 h, the water were collected and replacedwith fresh water. This procedure was daily repeated for 23 days. Releaseof the oligonucleotides into the collected water samples was evaluatedby measuring the FAM (5 carboxy-fluorescein) fluorescence byquantitative fluorimetry. (Excitation wavelength—485 nm, Emissionwavelength—520 nm). The concentration of the ssDNA released was measuredaccording to a standard curve plotted (Fluorescence vs. oligonucleotideconcentration, FIG. 1). A linear standard curve was obtained in therange of 0.05-25 pmole/μl. Percentage of the oligonucleotide releasedwas normalized to the estimated amount of the oligonucleotides loadedinto the matrix.

FIG. 2 shows that after 1 hour, about 20% of the loaded ssDNA arereleased into the water. Thus, this figure clearly demonstrates that theabsence of PEG in the oligonucleotide solution negatively affect theamount of ssDNA loaded into the fatty matrix. Thereafter, in the nexttwo days similar amount was released (˜10%). From day 5 until day 16, azero order release of the ssDNA was observed; in average 1-1.8% of theaccumulated ssDNA was released every day. From day 16 there was adecrease in the release of the ssDNA until day 23 when the ssDNAconcentration in the sample was under the detection limit.

Samples were also examined under light microscopy (×400). As shown inFIG. 3A there was a typical type of lipid vesicles released into themedium following hydration. FIG. 3B shows a green fluorescence emissionfrom the same vesicles indicating that these vesicles contained theflorescence probe.

Example 4 Testing the Functionality of the Released Oligonucleotides

The ssDNA loaded into the matrix (having the nucleic acid sequence setforth in SEQ ID NO:1) was designed as a forward primer to amplifyfragment of the murine housekeeping gene GapDH. Reverse primercomplimentary to the gene was also prepared, consisting of the nucleicacid sequence GGATGACCTTGCCCACAGCCTTG (SEQ ID NO:2). After theconcentration of the released ssDNA was evaluated, 100 pmole of thereleased oligonucleotides from different time points were taken for aPCR reaction. cDNA derived from mouse spleen was used as a template. Theoligonucleotides released from the matrix and the reverse primer wereused to amplify a GapDH fragment with an expected size of about 500 bp.The PCR reaction was performed using ReadyMix™ (Sigma) components.

FIG. 4 shows agarose gel of the PCR products. The expected 500 bpfragment was obtained, confirming that the ssDNA released at all timepoints tested were active and capable of amplifying the correct genefragment.

The size of the ssDNA released at the several time points was sent tosize evaluation by GeneScan analysis. Samples of ssDNA released after 1,2, 5, 7, 9, 12, 14, 16 and 20 days were tested. In all samples exceptthose obtained at 14 and 16 days intact oligonucleotides with the sizeof 23 bp were detected (FIG. 5). The differences in the peak intensitiesare due to the concentration of the ssDNA in the sample and the qualityof precipitation of the DNA from the released complexes. The firstobserved peak is probably due to the purity of the oligo (it was cleanedby desalting).

Example 5 Preparation of a Matrix Comprising Nucleic Acids with PEG

Matrix Preparation

Stock Solutions:

Stock solution 1 (SS1): PLGA 75/25, 300 mg/ml in ethyl acetate (EA).

Stock solution 2 (SS2): Cholesterol (CH), 30 mg/ml in EA.

Stock solution 3a (SS3a): Single strand DNA oligo (23 mer, having thenucleic acid sequence set forth in SEQ ID NO:1), labeled with FAM at the5 prime, 0.5 mM in DDW.

Stock solution 3b (SS3b): Polyethylene glycol 8000 (PEG 8000) dissolvedin Stock solution 3a (PEG final concentration 250 mg/ml).

Stock solution 3c (SS3c): Stock solution 3b diluted ×10 into MeOH:EAsolution (v/v); (ssDNA 0.05 mM; PEG 25 mg/ml).

Solution A was obtained by mixing 0.2 volume of SS1 with 1 volume of SS2(PLGA 50 mg/ml, CH 25 mg/ml).

Solution B contained phospholipids (DPPC, DMPC, DSPC or DPPC/DPPE 9:1w/w) dissolved in SS3c, comprising the ssDNA and PEG.

Solution AB was obtained by mixing 1 volume of solution B with 1.5volumes of solution A by vortex and incubating the mixture at 45° C. for5 minutes.

Coating

100 mg of commercial artificial bone substitute (tricalcium phosphateparticles, TCP) were coated with 0.25 ml of the matrix solution(solution AB). The solvents were evaporated by incubation at 45° C. for1 h of until no liquid is visualized, followed by overnight vacuum.

Example 6 Release of ssDNA from the Matrix Prepared with PEG

TCP particles coated with the matrix comprising the FAM-labeled ssDNAprepared as described in example 5 above (including incubation of thessDNA with PEG) were hydrated with water and incubated at 37° C.

After 1 h, the water were collected and replaced with fresh water. Thisprocedure was daily repeated for 40 days. Release of theoligonucleotides into the collected water samples was evaluated bymeasuring the FAM fluorescence as described in Example 3 hereinabove.

The effect of the duration of the incubation time of ssDNA with PEG onthe release of ssDNA from the coated particles was also examined:

Stock solution 3b (PEG 8,000 dissolved in water solution of the ssDNA)was diluted into MeOH/EA after one hour of incubation (short incubation)and after 18 hours of incubation (long incubation).

FIG. 6 shows the accumulated amount of the released ssDNA over time.From this figure, it is clearly demonstrated that (i) the presence ofboth the polymer and the lipid component are necessary in order toobtain graduate slow release of the ssDNA from the matrix: in theabsence of the lipid (DPPC in the particular example) most of the ssDNAis immediately released into the hydration water; and (ii) longerincubation time of the oligonucleotide with PEG results in longerrelease period of the nucleic acids once the matrix is hydrated.

Example 7 The Influence of the Phospholipids Composition on the ReleaseRate of ssDNA

The influence of the phospholipids type and particularly of the lengthof the phospholipid acyl chains on the rate of ssDNA release from thematrix of the present invention was also examined. FIG. 7 demonstratesthat the longer the acyl chains, the lower is the rate of ssDNA release,with DMPC (14:0)>DPPC (16:0)>DSPC (18:0). In the case of DMPC most ofthe ssDNA is released within the first five days. In contrast a matrixprepared with DPPC released the ssDNA in steady rate (zero order) up to30 days. In the case of DSPC the rate of release is significantly lowerthan the other two phospholipids.

Thus, the release rate of ssDNA from the matrix of the invention can becontrolled by the phospholipids composition.

The foregoing description of the specific embodiments will so fullyreveal the general nature of the invention that others can, by applyingcurrent knowledge, readily modify and/or adapt for various applicationssuch specific embodiments without undue experimentation and withoutdeparting from the generic concept, and, therefore, such adaptations andmodifications should and are intended to be comprehended within themeaning and range of equivalents of the disclosed embodiments. It is tobe understood that the phraseology or terminology employed herein is forthe purpose of description and not of limitation. The means, materials,and steps for carrying out various disclosed functions may take avariety of alternative forms without departing from the invention.

The invention claimed is:
 1. A substrate at least a portion of thesurface of which is coated by a matrix composition comprising: a. abiocompatible polymer comprising a polyester; b. a first lipid componentcomprising at least one lipid having a polar group; c. a second lipidcomponent comprising at least one phospholipid having fatty acidmoieties of at least 14 carbons; d. at least one nucleic acid basedagent; and e. polyethylene glycol (PEG); wherein when maintained in anaqueous environment the matrix composition provides sustained and/orcontrolled release of the nucleic acid based agent.
 2. The coatedsubstrate of claim 1, wherein the substrate to be coated includes atleast one material selected from the group consisting of carbon fibers,stainless steel, cobalt-chromium, titanium alloy, tantalum, ceramic,collagen, gelatin and tri-calcium phosphate.
 3. The coated substrate ofclaim 1, wherein the PEG is a linear PEG having a molecular weight inthe range of 1,000-10,000.
 4. The coated substrate of claim 1, whereinthe lipid having a polar group is selected from the group consisting ofa sterol, a tocopherol a phosphatidylethanolamine and derivativesthereof.
 5. The coated substrate of claim 3, wherein the sterol ischolesterol.
 6. The coated substrate of claim 4, wherein the cholesterolis present in an amount of 5-50mole percent of the total lipid contentof said matrix composition.
 7. The coated substrate of claim 1, whereinthe second lipid component comprises a phospholipid selected from thegroup consisting of phosphatidylcholine or a derivative thereof; amixture of phosphatidylcholines or derivatives thereof; aphosphatidylethanolamine or a derivative thereof; and any combinationthereof.
 8. The coated substrate of claim 1, further comprising acationic lipid selected from the group consisting of DC-Cholesterol,1,2-dioleoy-3-trimethylammonium-propane (DOTAP),Dimethyldioctadecylammonium (DDAB),1,2-dilauroyl-sn-glycero-3-ethylphosphocholine (Ethyl PC),1,2-di-O-octadecenyl -3-trimethylammonium propane (DOTMA) and anycombination thereof.
 9. The coated substarte of claim 1, wherein thebiocompatible polymer further comprises a non-biodegradable polymer. 10.The coated substrate of claim l, wherein the polyester is selected fromthe group consisting of PLA (polylactic acid), PGA (poly glycolic acid)PLGA (Poly (lactic co glycolic acid) and combinations thereof.
 11. Thecoated substrate of claim 9, wherein the non-biodegradable polymer isselected from the group consisting of polyethylene glycol (PEG), PEGacrylate, PEG methacrylate, methylmethacrylate, ethylmethacrylate,butylmethacrylate, 2-ethylhexylmethacrylate, laurylmethacrylate,hydroxylethyl methacrylate, 2-methacryloyloxyethylphosphorylcholine(MPC), polystyrene, derivatized polystyrene, polylysine, polyN-ethyl-4-vinyl-pyridinium bromide, poly-methylacrylate, silicone,polyoxymethylene, polyurethane, polyamides, polypropylene, polyvinylchloride, polymethacrylic acid and combination thereof.
 12. The coatedsubstrate of claim 11, wherein the biocompatible polymer comprisesco-block of a biodegradable polyester and a non-biodegradable polymer.13. The coated substrate of claim 1, wherein the weight ratio of totallipids to the biodegradable polymer is between 1:1 and 9:1 inclusive.14. The coated substrate of claim 1, wherein said matrix composition ishomogeneous.
 15. The coated substrate of claim 1, further comprising atleast one compound selected from the group consisting of a sphingolipid,tocopherol, a free fatty acid having 14 or more carbon atoms, apegylated lipid and an additional phospholipid selected from the groupconsisting of a phosphatidylserine, a phosphatidylglycerol, and aphosphatidylinositol.
 16. The coated substrate of claim 1 wherein thenucleic acid based agent is selected from the group consisting of:plasmid DNA, linear DNA selected from poly and oligo-nucleotides,chromosomal DNA, messenger RNA (mRNA), antisense DNA/RNA, RNAi, siRNA,microRNA (miRNA), ribosomal RNA, oligonucleotide DNA (ODN) single anddouble strand, siRNA, imunostimulating sequence (ISS), locked nucleicacid (LNA) and ribozyme.
 17. A method of administering a nucleic acidbased agent to a subject in need thereof, said method comprising thestep of administering to said subject a coated substrate according toclaim
 1. 18. A method of producing the coated substrate of claim 1comprising the steps of: a. mixing into a first volatile organic solvent(i) a biocompatible polymer and (ii) a first lipid component comprisingat least one lipid having a polar group; b. mixing polyethylene glycolinto a water-based solution of the nucleic acid agent; c. mixing thesolution obtained in step (b) with a second volatile organic solvent anda second lipid component comprising at least one phospholipid havingfatty acid moieties of at least 14 carbons; d. mixing the solutionsobtained in steps (a) and (c) to form a homogeneous mixture; e. mixingthe homogeneous mixture obtained in step (d) with a substrate; and f.removing the volatile solvents and water.
 19. The method of claim 18,wherein step (c) further comprises (i) removing the solvents byevaporation, freeze drying or centrifugation to form a sediment; and(ii) suspending the resulted sediment in the second volatile organicsolvent.
 20. The coated substrate of claim 1, wherein at least 30% ofsaid nucleic acid based agent is released from the composition at zeroorder kinetics.